An association or club of people who share the same hobbies or interests; often formed at schools or in local communities.
大学では写真同好会に入って、週末に撮影に行っている。
At university I joined the photography club and go shooting on weekends.
地域の同好会が毎月集まって作品展を開いた。
The local club of enthusiasts met monthly and held an exhibition of their works.
初心者歓迎の同好会なら、気軽に参加できますよ。
If it's a beginner-friendly club, you can join casually.