The Astrological Houses are divisions in the birth chart which relate to different areas of the environment around us and are where we express all matters related to this particular area of life. The 1st house begins at the Ascendant, or AC, and is where we develop and nurture our self-image; the 7th house, which is opposite, is where we meet one-on-one with others, encountering them and forming partnerships of various kinds with them.
People with planets in the 1st house may be very self-aware or at least open to learning and knowing more about themselves. They probably won't define themselves through the expectations of others as they already have a strong sense of who they are or of how they would like to become. A focus of planets in the 1st house is shown in this chart.
People with planets in the 7th house may be very outgoing and sociable, not liking to be alone or without others to refer to, as they tend to define themselves and learn about themselves through their interactions with others. This chart shows a focus of planets in the 7th house.
The ideal is to gain some balance between the 1st and 7th houses if we have an excess of planets in one of these two houses. Of course, it's not as simple as that and everyone is different, so a chart session with a qualified astrological consultant who uses astrological psychology will offer help and guidance to anyone who wants to take their understanding and personal development further. Find one by clicking on the appropriate tab at the top of the page. You can see me talking about the 1st and 7th houses here, and about all the other houses on my Astrochat Channel on YouTube.
For more info on the houses, all aspects of astrological psychology and how to learn about this for yourself, visit the Astrological Psychology Association website.