A:Answer They are sort of the same thing. You really cannot buy FRS radios any more. GMRS radios, however, also work on FRS frequencies. There are seven FRS channels, and modern GMRS radios cover those frequencies, but at FRS power limits (1/2 watt). There are seven channels that are shared between FRS and GMRS, but you need a GMRS license to use high power. There are seven channels that are GMRS only.
FRS and GMRS radios can talk to each other as long as the GMRS radios only use FRS frequencies -- plus the numbers on the display might be different.
Wikipedia has a nice summary of GMRS -- just search.
I hope this helps.