Bond beams are courses of block constructed with special units designed to receive horizontal reinforcement and grout.
These units are used to integrate the horizontal reinforcement with vertical reinforcement bars in a reinforced masonry wall.
Bond beams often are placed at regular intervals in the wall to permit placement of more reinforcement than would be possible using bed joint reinforcement.
Bond beams are used in masonry bearing walls–to serve as horizontal members along the top of the walls, tying the walls together.
Here it is in illustration.
And here is the application.