The conjunction, opposition, and square aspects are called hard aspects. The reason is they all compel action.
In the case of a conjunction, planets gang up in the same sign, aggregating a force that is simply not going to sit still. It is going to express itself. The only question is, how will the planets work with each other: is the conjunction a coalition of like forces (eg. Sun with Mars), or a compromise forged between forces that see things differently (e.g. Mars and Saturn). In either case, being in the same sign, the participating planets are bound by a common cause, so they have to find a medium ground for expression, and most likely they will.
An opposition is akin to an out-and-out conflict between opposing forces, because they occur between planets in opposite signs. Opposite signs are of the same mode, but different elements. For instance, Gemini and Sagittarius are in the same, mutable mode, but Gemini is an air sign, while Sagittarius is a fire sign. Signs in different elements believe in different things, even though they may express their beliefs in the same way if they are in the same mode. This antithesis in beliefs leads to a strong internal polarization, and the individual is caught in the middle.
It is very hard to hold opposing beliefs and still function normally–very few people are able to do it with full conscious awareness. As a result, there is often a side being taken: an Aries-Libra opposition might have the individual take the side of Aries and ignore Libra, and vice versa. Sometimes they might switch sides, fully being one or the other. And when you take one side and completely disown the other, you see the other side appearing in your life in the guise of a person with whom you have a deep conflict, mirroring the internal conflict that is insisting on being heard and lived.
Like the opposition, the square aspect also occurs between planets that are in signs of the same mode, but different elements. The only difference is that these signs are not in opposition to each other, so they are not facing off in a direct conflict. It’s more like forces that want to be left alone to go their own way, rather than engage in a direct tug-of-war. So the action that is compelled in this case is more of a niggling discomfort that never quite goes away unless both sides are accommodated as much as possible. In the case of the opposition the disowned side can be named as the other person and fought against, while that luxury is not available to the square. An integration is called for, and often, squares result in remarkable achievements borne out of a tremendous expressive effort to marry forces at odds with each other.
The trine aspect, by contrast, is a soft aspect. It occurs between planets that are in signs of the same element, separated by 120 degrees within an acceptable orb. Since the planets involved are in the same element, they play well with each other, with a sense of ease and comfort, without grating on each other as might happen in a conjunction. The upside of free expression without hindrance results in a natural talent or easy skill that can serve as an uplifting energy that fulfills the individual. The downside is that the person might never be compelled to act on this in any productive way because there is no external agency or internal discord that prompts action. Any action that might be taken is entirely up to the individual.
Let’s look at Steve Jobs’s horoscope and identify the trines in it, if any:

Start with the fire element, and look for all the planets in Aries, Leo, and Sagittarius that are within acceptable orb of separation. Moon and Mars are in Aries, Pluto is in Leo, no planet in Sagittarius. Mars is trine Pluto, within an orb of around 5 degrees. Moon is too far out of orb for a trine with Pluto.

Mars-Pluto aspects are generally indicative of a ruthless (Pluto) application of energy (Mars). It can also signify rage and violence (Pluto’s extreme expression drawing out the Mars anger to its fullest)–other restraining energies will need to be applied to prevent this from getting completely out of hand. Since we have a trine here, there is a better than even chance that the energy application doesn’t get out of hand because there isn’t any underlying sense of conflict or discord.
Next, the earth element. Venus is in Capricorn, but it can’t make a trine because there is no planet in Taurus or Virgo.
In the air element, there is Neptune in Libra and Mercury in Aquarius. But the orb is 14 degrees (if Mercury were at 28 degrees of Aquarius, it would be a 120 degree separation), so is this a little too much to qualify as a trine?

This is the kind of situation where we need to stretch the interpretation a bit. The general rule of thumb is to allow an orb of up to 10 degrees, but human life is not cut-and-dried like that, and the energies that animate us do not obediently follow the rules of geometry. There isn’t some kind of abrupt fall of after 10 degrees of separation, but a gradual waning. But if support is found in other quarters than even the energy of a greater than 10-degree orb can manifest quite clearly in the life.
In Jobs’s horoscope, the Sun is in Pisces. This means Jobs’s very identity, his reason to exist as it were, is of a Piscean nature, filled with visionary dreams and a strong identification with the felt needs of everyone. The planet that Mercury reaches out to aspect, Neptune, rules Pisces. So you could say that the Mercury has the support of the Sun through Neptune, and the aspect gathers energy and becomes highly relevant. If there is one word that can be used to describe Steve Jobs’s life work, it is “visionary”. This Mercury-Neptune trine was a driving force in articulating (Mercury is communication) that vision to the world.
Lastly, are there any trines in water? Sun is in Pisces, Jupiter-Uranus are conjunct in Cancer, and Saturn is in Scorpio. Since Jupiter, Saturn, and Uranus are planets with long orbital cycles, their sign position is shared by many people born in the same year, or even in the same generation. This means aspects between them will be impersonal, and not of relevance to the individual. So the only possibility here are trines from the Sun to these planets.

As with the wide orb Mercury-Neptune trine, the Sun is 15 degrees or more out of orb with any of the other planets. Should we still accept these as trines? A related point that I want to make here is this: in Vedic astrology, aspects are formed between planets without any notion of orb. The aspects are defined differently than in Western astrology, but whether an aspect is formed or not simply depends on whether there are planets in the signs that define the aspect. Once that is established, how strong the aspect is depends on the orb, but there is no formal definition of the orb. It is just a question or relative closeness or distance. Much depends on the importance of the participating planets, and supporting factors.
Ultimately it comes down to a question of degrees, and relative importance of all the aspects in the horoscope. In this case, given the singular importance of the Sun, the fact that if the Sun were to be taken out there is no other water trine, and the fact that the Sun makes 3 trines, I would accept these trines, and consider them to be quite important in the life expression. The Sun-Saturn trine imparts a quality of business (Saturn) acumen (Sun), expressed in the form of “soft” vision and emotional manipulation (water, Pisces, Scorpio) – Jobs famously got John Sculley to quit as president of Pepsi to run Apple, with this one question: “Do you want to sell sugar water for the rest of your life or come with me and change the world?”
The Sun-Jupiter/Uranus trine adds a good bit of bombast and emotional confidence to the personality, which was clear to see in Jobs’s conviction in his beliefs, and his almost irrational confidence that the world would eventually come around to his point of view. “You can’t just ask customers what they want and then try to give that to them. By the time you get it built, they’ll want something new.” He made his mark out of an enormous belief in sussing out (a very watery thing) what people might want, and building it, well before even they knew it themselves.
Find out the trines, if any, in your horoscope. Only consider trines in which at least one of the planets is the Sun, Moon, Mercury, Venus, and Mars; ignore all others. Use orbs as needed, with the above discussion in mind about qualitative assessment of importance. Interpret according to the element of the participating planets (whether fire, earth, air, or water) and the significations of the planets. Start with what you consider to be your strengths and talents, and then match them to the trines. Doing it this way will also tell you which trines are stronger than others, which will also then give you a good idea of which elements and planets you “own” more than others.