Poe is a chat app made by Quora that puts AI chatbots from many different companies in one place. Instead of opening one company's app for one AI, you open Poe and choose which one to talk to. Poe's own help pages list bots from OpenAI, Anthropic, Google and Meta, alongside image, video and audio generators.
Each of those AIs runs on a model (the AI "brain" that does the actual thinking), and the model belongs to the company that built it, not to Poe. Poe's terms say plainly that Quora does not create what the bots write. Poe is the front door and the bill; the thinking happens elsewhere.
The reason to use it rather than one company's own app is comparison. Poe's app listing describes comparing answers from different AIs and combining bots "all within a single chat thread," so you can see for yourself which one suits a task instead of taking anyone's word for it.
Anyone can also build a bot of their own on top of an existing one, and other users publish theirs. That is why Poe's bot list is much longer than the handful of big-company AIs — many of the bots you will scroll past were made by individuals, not by the companies whose models they use.