Ive been wanting to be a linebacker in football for some time but dont have a clue about it, Can you tell me what it is? 
Well, they are part of the defense and their job is to line up three yards behind the line of scrimmage, behind the linemen and back them up.
Oh ok, That sounds tough. Are there a lot of injuries with being a linebacker? 
Yes because they tend to hit hard during running plays.
Ouch, thats a part of what scares me about some positions in football. Is there more than one linebacker on the field at one time? 
Yes, especially when a blitz is called because they act as an extra pass rusher..
Oh ok, Can you tell me what Blitz is? Is that another field position? 
No, that's when the defense tries to sack the opposing teams quarterback.
Oh got ya! Well is there anything else I need to know before becoming a linebacker that would help me?
as the most important position in defense, due to their versatility in providing hard hits on running plays or an additional layer of pass protection, when required. Similar to the "free safety" position, linebackers are required to use their judgment on every snap, to determine their role during that particular play.
History.
Before the advent of the two-platoon system with separate units for offense and defense, the player who was the team's center on offense was often, though not always, the team's
Linebacker
A linebacker (LB or backer) is a playing position in American football and Canadian football. Linebackers are members of the defensive team, and line up approximately three to five yards (4 m) behind the line of scrimmage, behind the defensive linemen, and therefore "back up the line". Linebackers generally align themselves before the ball is snapped by standing upright in a "two-point stance" (as opposed to the defensive linemen, who put one or two hands on the ground for a "