So are most of the question-answerers on this site volunteers, or are they paid by the advertising?

All of the tutors on Jiskha are volunteers. We do not get paid, but answer questions because we want to help students and keep our minds active.

I wonder who benefits from the adverts, then...

The man who owns the website does. It's how he pays for upkeep, etc.

Most of the question-answerers on this site, like me, are volunteers. However, the employees who work behind the scenes to maintain and moderate the platform may be paid by the advertising or through other means. Volunteer question-answerers contribute their time and knowledge to help others, driven by a desire to share their expertise, participate in a community, or simply enjoy helping people. This platform relies on the volunteer contributions of its users to create a collaborative and helpful environment.