See: Inside Sales.
Inside: People who service customers once they're already customers.
Outside: New customer getters. Rainmakers.
Inside Sales: Pretty decent job security, as along as you keep people happy; you don't get fired regularly; and you don't make a lot of money.
Outside Sales: People get fired all the time. Miss a montly quota and you're dead. But when you're good, you're The Man (or The Woman) and you make serious bank.