Hypercorn supports asyncio, uvloop, or trio worker classes thereby allowing ASGI applications writen with these in mind to be used.
Asyncio is the default event loop implementation that is part of the standard library. It is relatively well supported by third party libraries.
Uvloop is a different event loop policy for asyncio. It is used as it is quicker than the asyncio default, however it does not work on Windows.
Trio is a third party event loop implementation that is not compatible with asyncio. It is less supported, however the API is much nicer to use and it is harder to make mistakes.