Can somebody explain the home grow rules in plain English

Second post from me and I am afraid it is another beginner question. My son keeps telling me I am allowed to grow a couple of plants at home now, and every time I try to confirm that for myself I end up in a document written for lawyers, or a forum post from someone in another state entirely. What I would like to know is what the actual limits are supposed to be, whether it matters that I rent, and where the reliable place to read this is. I am not asking anyone here to be my solicitor and I would not treat a reply as one. I would just like to be pointed at something official that a person can read. I have a very sunny south window and a lot of newly free time. That is the extent of my qualifications.