As with any Mitzva in the Torah, there are many reasons and insights. The deeper something is the more ways there are to bring it out.
The basic idea is, as it says in the Torah: “With this you will remember that I sat you in booths when you left Egypt.” This refers to the clouds that surrounded us to protect and hide us, or to actual Succos according to some. But, as with all Mitzvos, we know that we don’t understand the full depth and reason.
Being in the Succah is being enveloped in a Mitzva of Hashem. After accepting Hashem’s kingdom and returning to Hashem with repentance, we go even further to be accepted by Hashem. Chazal say that on Succos we leave our permanent dwelling to enter a temporary one. We are realizing and playing out the fact that this world is only a anteroom to the world to come.
With the Succah we focus on the fact that we are under the protection of Hashem and that the whole world belongs to him.