SPS is a shorthand for “SharePoint Saturday”. SharePoint Saturdays are community-led local events, that typically draw in mainly local attendees to meet vendors from around the globe and listen to sessions by speakers, many of whom have traveled from far away. Typically, though, the local community is represented in not only the audience but also vendors and speakers.
I’ve attended quite a few SharePoint Saturdays, my employer has been sponsoring many of them, and I’ve spoken in some as well. If you only want to see the sessions I’ve spoken at, see this page: https://www.koskila.net/tag/sessions