Generally used by military personnel to convey that they already understood something that was said to them.
Useful when you want to tell someone who's a higher rank than you that you already knew what they just told you, and you're kind of
pissed that they thought you didn'
t already know, but the ridiculous stipulation of having to answer to a grown man who's only been in a year or
two longer than you dictates that you can't have an
opinion of your own, much less tell this man to piss off.
Disclaimer: is also used casually/
non-aggressively, but its main appeal is that you can get away with being belligerent.