My position is linebacker.
Linebackers are defensive positions in football. How long have you played football? 
I have been playing since I was 6.
History of American football positions
American football positions have slowly evolved over the history of the sport. From its origins in early rugby football to the modern game, the names and roles of various positions have changed greatly, some positions no longer exist, and others have been created to fill new roles.
Origins in rugby.
Being variants of 19th century rugby football, American and Canadian football position nomenclature has its origin there. Early rugby did no more than distinguish in tactics between the great bulk of the players who
of the same position. The positions were later renamed "linebacker". However, that did not become the usual way to name that position until platoon football became common, with players specializing in offense or defense, substituted according to which team has the ball. There seems to have been some tendency for defensive positions to be named for where the player would play on offense, although quarterback and safety formed an early exception.
When linebackers are playing close to or level with the line, a somewhat reliable way to distinguish