A retaining wall is a structure designed and constructed to resist the lateral pressure of soil, when there is a desired change in ground elevation that exceeds the angle of repose of the soil. For example a basement wall is one kind of retaining wall. But the term usually refers to a cantilever retaining wall, which is a freestanding structure without lateral support at its top. We will use blocks to create a retaining wall in your backyard and get the desired look and wall which you want. A foundation wall is the masonry or concrete walls which are below ground level that serve as the main support for a structure.