Captioning

Captioning and transcripts are a valuable tool for Deaf and hard of hearing individuals. A transcript is a document with the text of the audio. Think of it kind of like a script. Whereas captions (closed captions, open captions, subtitles) appear a few words at a time in conjunction what people are saying.

There is captioning that is done by a real person, like CART services you'd see in court. There is also captioning that is automatically transcribed. 

There are also ways to access captions and/or a transcript, even if it's not embedded in the video or audio, however, part of that also depends on which device you are using.