Can you invite other people to aa?

Yes and no. Support groups like aa have both open and closed meetings. Members are encouraged to bring friends to open meetings for a variety of reasons, the least of which being to support you better or to help them to begin recovery. The closed meetings are just that, closed to members only. This is to foster a safe place for sharing, which is important to the recovery process.
Depends. Some meetings are what are called "closed." they are only for people who have alcohol problems. Other meetings are "open, " and anyone can attend. When they go around the room and introduce themselves, a person who is not alcoholic can either pass, or say "i'm judy, and I'm curious." there are meetings for friends and loved ones of the alcohol troubled person, alanon; your friend can attend.