A tb is a rb. A rb is a tb. Fb & hb are specific.
What is Tailback?
A position on offense that lines up in the backfield and is primarily responsible for running with the football. The tailback is also responsible for catching the ball out of the backfield, and helping to block on passing plays. The tailback will most often line up behind the quarterback, although will line up next to the quarterback in shotgun formations. Tailbacks are often faster and more agile than other backs, and will have the highest rushing statistics on a team under most circumstances.