Live close captioning is a test feature in Teams. When active by the end user it will produce captions for that user. This text appears a few seconds after it is spoken and is fairly accurate. The close captioning is only in English and will miss proper nouns or technical terms.

1) When in a meeting on the menu bar select the More actions icon

2) In the menu at pops up select Turn on live captions (preview)

3) After a few seconds close captioning will start on the bottom left of the screen.