You can grow it in a closet. The idea is to be able to capture the humidity but also to be able to control that humidity as well. Cannabis gets very pungent. It is unmistakable. This is especially true in flower stage. You should really look at the entire process from on of the journals to get a sense of it. In a tent you have access ports to bring in logistics like electricity for lighting and air circulation. You will also want to have a exhaust vent with a canister filled with charcoal to remove the smell and that helps with humidity as well. You will also want a place you can control the lighting if you are not growing an autoflower. If you are growing a photo they need a light sequence trigger to begin to flower. That is when the lights get a 12/12 cycle. They go through a large stretch during flower and require lots of food and water to be really productive.
I suggest reading also the guides here on this site. There is so much to growing weed that I didn’t know about until I started.
Here is my first grow journal. You can watch me do some mistakes and some good things and it also shows my set-up. I have a 4x4x82. I was planning to grow 4 then it turned to two. Now it is going outside because… long story. It is in my grow journal.