Lightning conductor is a device that protects tall building from lightning .It has a spike at top which is a metal and a copper plate at bottom. As lightning occurs it transfer the charges to the ground safely. That's how it plays a major role in protecting tall buildings.
Lightning conductors are not put up to get hit by lightning as such. They can and do get hit by lightning but the expression "conductor" is a misnomer. 

They act as a discharge to ground to prevent the buildup of static charge in an approximate "sphere" from the tip of the rod to the surrounding ground. Any lightning strike will tend to go across the surface of this sphere and provide protection for the people under the sphere. Thus standing near the tall building usually gives complete protection. The taller the building the better and wider is the protection