TL;DR: =
Too Long; Didn’t Read:

What does it mean?

Too Long; Didn’t Read:
In other words: In case you were falling asleep reading through the full length version, here’s the recap in bulletpoints.

Example:

I write a lot on LinkedIn, others do as well. Whenever you on the move scrolling through your feed, you just might not want to read very lengthy articles or posts (goes for all social platforms actually). It simply isn’t as comfortable. Plus in some cases your attention span simply is drained, so adding a TL;DR: to the bottom still gets 80% of the message across.

Where else would this do magic? Exactly, all the very lengthy work emails.