Blocking

Most martial arts employ some form of blocking technique.
But what is a 'block'?
A block is an attempt to stop the path of incoming force.

The opponent punches to your face and you raise your arm to prevent the fist hitting your face.
Instead of hitting your face, the fist misses.
The impact of the blow passes through the arm.

Blocking may indeed stop you from being hit, but it has certain drawbacks.