What is an APX?

Excuse me, could you please elaborate on what an APX is? I've heard the term mentioned in the context of cryptocurrency and finance, but I'm not entirely clear on its exact definition or purpose. Is it a specific type of token, a protocol, or something else entirely? Could you provide a brief overview of its key features and how it fits into the broader cryptocurrency and financial landscape? I'm quite interested in learning more about this particular topic.