The photo below is of a footing that was recently poured for a custom home that we are building in Central Phoenix. (A footing is a foundation usually out of concrete that is used as a base to support the weight of your house. ) Many houses start out this way unless they are using a Post-tensioned slab. (We can discuss that at another time.) You can see rebar coming out of the footing that will provide a connection between the footing and the stem wall.
The stem wall is used to raise up the outside perimeter of your house to the future level of your floor. (See Photo below)
In the photo above, you will notice a channel running through the top row of block. This channel is an opening for the masons to place horizontal rebar into. When grouted, (filled with concrete) that top row of block is called a bondbeam. A bondbeam adds strength to a wall. It combines the weight bearing properties and rigidity of block, with the strength and bendability of rebar.