Dislocations-Linear Defects         

Dislocations are abrupt alters in the regular ordering of atoms, along a line (dislocation line) in the solid. They occur in high density and are very important in mechanical properties of material. The Burgers vector, found by doing a loop around the dislocation line and noticing the extra interatomic spacing required to close the loop, characterizes them. The Burgers vector in metals points in a close packed direction. 

Edge dislocations happen when an extra plane is inserted. The dislocation line is at the end of the plane. In an edge dislocation, the Burgers vector is perpendicular to the dislocation line.