The fourth house is one of the four angular houses, the others being the 1st, 7th, and 10th. Angular because the cusp of the 4th house is the IC, which is one of the angles of the chart. The primary signification of the 4th house is the home.
At the most mundane level, home is the house in which you live. At the psychological level, it is the idea of home, what home means to you. This is signified by the sign on the cusp of the 4th house, which is to say the sign of the IC. For someone with Sagittarius on the IC, given the wandering nature of the Sagittarian, home could be wherever they hang their hat. But for a person with Taurus on the IC, it is a place of peace and quiet, with possibly a great room that looks out into the woods.
The word home stands for a lot more with regard to the 4th house. It’s our ancestral roots, starting with our parents, and expanding out to the extended family, tribe, culture, even country. It stands for our origins, the material out of which we emerged. These significations are mostly derived from the sign of Cancer, which is the ruler of the natural 4th house. Some astrologers tend to associate the mother with the 4th house, others, the father.
Clearly, there is some ambivalence here. If we stay with the Cancer signification of nurturing, then the 4th house should be traditionally associated with the parent who was the primary nurturer in the home, the one who shaped us culturally. On the other hand, if we associate the 4th house with the parent who shaped our greater world-view, then traditionally the father takes ownership of the 4th house more so than the mother. The dichotomy simply suggests that which parent resonates with the 4th house differs from person to person.
Planets in the 4th house are extremely significant because of their outsize influence on your early upbringing, which impacts our life well into adulthood. For instance, Mars in the 4th house might suggest a childhood home that saw a lot of activity, or was a kind of battleground; Saturn might suggest a restrictive childhood with many constraints or a parent who was cold and authoritarian; Uranus might suggest early upheaval that left deep scars. Remember that while the actual state of the home may have been the same, different siblings grow up in the same household may have different takes of their parents or their childhood, which you can observe by analyzing the 4th house of the individual siblings.
The impact of the outer planets in the 4th house has a particularly significant and far-reaching influence on childhood and development.
US Vice President Kamala Harris has a packed 4th house, with the outer planets Uranus and Pluto (and Venus) in it.

Early childhood brought forth a Uranian upheaval–her parents divorced when she was seven. Moreover, the Uranus-Pluto combination of norm-breaking action (Uranus) that is taboo or transformative (Pluto) is evident in the extreme difference in race and background of her parents: her father was a Black Jamaican and her mother was a Tamil woman from India. This would have compelled Harris to ask lifelong questions about her parents, her early home, and her roots, in her quest to come to terms with these powerful 4th house issues.
Prince Charles of the UK has Neptune in the 4th house in very close contact with the IC (and also Venus, Mercury, and the Sun).

His childhood, therefore, must have had a significant Neptunian influence. Among other things, Neptune signifies disappearance: Charles’s parents were hardly there because he was raised largely by nannies. Later he was sent way to boarding school despite his protests. The long absence of a parent in early childhood leaves a hole in the child’s perception of that parent, and this hole is filled by a mythical, larger-than-life figure who may not be anything like the actual parent. Charles hero worshipped his father, so it appears that the Neptunian myth-inducing fantasy was attached to the father figure.
Actress Liv Tyler has Pluto in the 4th house.

In her case, the Pluto signification of secrets (an amplification of the basic Pluto suggestions of things that lie hidden beneath the surface) is connected with the 4th house. Her mother, while living with rock musician Todd Rundgren, had a brief affair with Steven Tyler, the more famous rock musician. Liv’s mother claimed that Rundgren was the father and Liv grew up not knowing otherwise, treating Rundgren as her father-figure. The secret was only revealed when Liv was around 11 years old, when she came to know that Steven was her biological father. It’s not hard to imagine her feeling betrayed (another Pluto signification) by her mother all those years.
For yourself, consider the sign on the cusp of the 4th house in your horoscope, and see if its significations resonate more with one parent or the other. The sex of the parent is irrelevant, what is important is to recognize and appreciate which parent played the role of nurturer and which parent shaped your world-view. And of course, in the case of a single parent, they would have had to play both roles. Or, the shaper of the world-view could be a parent-figure, like an uncle or aunt, and not a biological parent.
Aside from parental significations, also think of what home means to you, what you need to call a place a home, what kind of atmosphere in the house makes it feel like home, and see how all of these resonate with the sign on the IC.