This is Meta's Model API developer portal, listed here under Llama 3.3. It gives developers access to Meta's models, with a playground to test them before building.
The portal currently highlights Muse Spark, aimed at long coding and agent tasks, and Muse Code, a multi-agent coding tool for the terminal on Mac and Windows. It also lists other models such as SAM. It suits developers who want to build with Meta's AI models.