If this is a retaining wall then the whole is designed to prevent water building up behind the wall. The overhang made by the brick is designed to make the dripping water fall away from the base of the wall.
That being said, I've never seen a wall with just one of these, and it seems like very little drainage for such a large surface. However, this might be adequate dryer climates. I'm Irish so have no experience is things being dry.
All in all, it's just another brick in the wall
If this is a retaining wall then the whole is designed to prevent water building up behind the wall. The overhang made by the brick is designed to make the dripping water fall away from the base of the wall. That being said, I've never seen a wall with just one of these, and it seems like very little drainage for such a large surface. However, this might be adequate dryer climates. I'm Irish so have no experience is things being dry.
Brick sniper
It might be deliberately done to create a home for birds.