Correct.
HLS and Dash are industry standards. Essentially the client downloads a file which lists the files in various bitrates and chunks and the client determines which is best for the given connectivity.
And even if you are using a "regular" video format like mp4, browsers will still use range requests [1] to fetch chunks of the file in separate requests, assuming the server supports it (which most do).
[1] https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Ran...