what is this about?

It's about SCP. A fictional secret organization whose goal is to capture anomalies and keep them locked up and away from human knowledge, while protecting normal humans any way possible. Each anomalies(or what we call SCP) is a story written by a single person or a collab by many. Basically the idea is a huge collaboration project in the internet.

You can just search what is SCP in YouTube and you'll find a whole lot of videos explaining it. Explorer Series' video does it best.