I don’t think so, but I could be wrong. I guess the “groups” functionality of Facebook could technically qualify it as such, but its primarily aimed at being a social media website. I’m not 100% on it either, because there’s a lot of overlap between platforms and their functionality.

It’s in the name, mostly. It aggregates content. You can post links, text posts, images to specific communities and have them displayed in a feed of your communities of choice. That’s what Digg was and Reddit is, and kind of what Lemmy is doing- except on the Fediverse.