"Session" is a common word used by everyone. It means almost the same as "meeting", except that sessions are generally more structured, deliberative, or regularly scheduled. If you meet every week for one hour with your yoga instructor, you could refer to those meetings as "sessions". "Photo session" does not have any special meaning. It's just a session for the purpose of taking photos. "Photo shoot" on the other hand is a specialized expression. Normal people don't use it much. It would be used by designers, advertisers, movie producers, and photographers doing commercial (not artistic) work.

A "photo shoot" is usually where top-level photographers take photos of models or actors for publication in print media or in advertising. A "photo session" just means a scheduled slot with a photographer who normally takes pictures of families, pets or individuals.