Some associations require their members to attend e.g workshops to collect credits. There's a minimum annual credits you need to collect otherwise you lose membership.
If it is how I think it is, then yes, it is a proof that you attended the event.
I'm not sure how it is in other countries, but in some countries (example: Brazil) some courses (like Computer Science) require you to have "additional hours", where these hours can be courses, lectures, etc related to the course.
To prove to the university that you did these courses, you need a certificate "proving" that you participated. Most of the time they are a PDF file with the name of the event, the date and your name in it.
