Well, it stands for Technical Service Bulletin.
Generally, it'* a notice to the dealer on how to handle an issue that has become common.
IO think it usually instructs them how to repair or fix a problem.
I imagine that most of the time you'll have to pay if it'* out of warranty. But, it'* pretty good ammunition to use to try and get it fixed for free.
I did find a TSB on a Windstar for front springs, and they replaced them for free after it was waaay out of warranty. (I think that it was a way to keep the owners satisfied on an as-need basis, to avoid a safety recall.