When the soils underneath your foundation fail to support the weight of your home, the foundation will begin to settle unevenly, and cracks will appear.
As vertical cracks form and the wall or corner of the house begins to rotate, you will typically see cracks that are wider at the top or bottom.
Foundation cracks that are caused by the settlement are very serious, and they will only get worse over time as the home continues to move. If you are concerned that your foundation may be cracking due to settlement issues, it's best to consult a professional right away.