Originally Posted by Desmodus
If my guess is right, its probably to identify your team members easier over radio comms instead of saying their name?
As far as I know, that's about it. Members of group/team/squad Alpha for evample will be given a callsigns in the following manner:
With alpha being Phonetic alphabet for A, you would see it written as:
This just carries over to other letters as well, look up phonetic alphabet if you want to see what it'd sound like in radio or vocal chatter