What is the history about the two headed eagle that some countries use on their flags or other governmental institutions emblem?

by JerkDoctor

It is in the Albanian flag, in the Serbian flag and in some other emblems that can't think of their names now. Is there a correlation? Where is the origin of the two headed eagle?

Searocksandtrees

hi! it might be worth x-posting this question to the flag sub, /r/vexillology, or /r/heraldry to see what they come up with. Meanwhile, here's an earlier post that may be of interest ~