Some basic uses: SSH, wake-on-lan, downloading youtube videos, watching anime through ani-cli, coding, pen-testing, setup your phone as a file server through copyparty, setup a full linux desktop on your phone, etc.

For anyone who already is familiar with a linux terminal, termux is a great way to use a lot of the open-source tools you're already familiar with instead of trying to find a dozen different apps instead (that all probably show ads, spy on you, or require a subscription). There are also several apps that use it as a necessary backbone for their functionality, and require it to be installed.