There are different looking cracks. If the crack is wider at the top of the wall and stepping down the bricks, diagnolly through the mortar, it is possible the foundation has settled unevenly. There may be a different soil condition under that parts of the foundation, the soil under the wedge breaking off is lower than the rest under the wall.
This same problem can cause a crack that runs parallel to the vertical edge of the wall, close to the top of the wall.
The split can only be an inch for every 40 feet of wall. Much more and it could be structurally damaged. If the cracks continue to grow you might lose the wall.
Cracks parallel to the ceiling of a foundation may be caused by heavy water saturated soil pushing it in. This may be a drainage issue and reinforcing the wall from the inside and forming a slope outside, that drains water away from the wall, can help.
If the cracks are from chipping of the surface in a wide area or cracking uniformly around the edges, you may have some chemical attack and the wall will get worse. This is possibly a water issue or the soil pH.