What is the difference between an inside linebacker and an outside linebacker?

To get things started, the outside linebackers are just that...they cover plays on the outside to prevent plays along the outer perimeter, thus the inside linebackers play witin the inside to prevent a blast and to blitz. It really all depends on which defensive play you are running....i.e. 3-4, 4-3, 46. If a 3-4 is called, you then have 3 very big linemen, and four linebackers. But within this formation, you have a strong side and a weak side. This is usually used to disguise where the fourth rusher will be coming from. The two inside LB's, one will cover the run while the other will drop back if needed. Hope this helps.