Teams has the option to enable closed captions during any call. This can be particularly helpful for the hard-of-hearing, but can also be useful for a wide variety of reasons. Here's how to enable them.
While you're in a call, select More on the toolbar. Then, go to Language and Speech, and select Turn on live captions.
After a few seconds, captions will begin to appear along the bottom of the window. These are only visible to you. Teams will show you who is speaking, and will attempt to transcribe what they're saying in real-time.
Please note that as with any automated system, this service is not 100% perfect - keep this in mind when using live captions.
At the far right-hand side, there's a menu which gives you a few additional options. You can change the language of the captions, as well as changing the spoken language - i.e. what language the members of the call are using.
To disable captions, go to the Language and Speech menu again as above, and select Turn off live captions.