When you build a home, you do not always have the option to build on a completely flat surface, nor is flat always the most aesthetically pleasing option. If you have large depressions in your yard, you will want to build them up so that water running off the roof of your house will run away instead of down into your foundation. On the other hand, a perfectly flat yard is not as visually interesting as a yard that has a contoured surface, such as those created with berms of dirt. When trying to shape the contours of your yard, you need to choose between topsoil and fill dirt.
Plants require a loosely packed soil with organic matter to provide nutrients in order to support stable growth. Thus, a good topsoil will have few to no rocks. The reason for this is that the rocks can make it hard for a plant to sink roots into the ground, and it is these roots that help the plant to survive on viciously hot days. Furthermore, topsoil should have minimal clay content and some mulch or organic materials mixed in. Clay soils tend to harden as they dry and this can make it hard for plants to grow. The organic content in a soil will decompose and release nutrients that plants can use to support growth.
On the other hand, when you are trying to fill a depression or build up a berm, you want a stable soil that will not settle too much as time goes by. If you use a soil that has a lot of organic content, the organic material will leave voids as it decomposes that can cause your fill to settle and leave depressions. Fill dirt will typically have a mixed composition of rocks and dirt. Rocks make an excellent fill material because they don't settle. They do not, however, necessarily create a surface that will support plant growth.
When you are preparing a yard for planting, your first concern should be making sure that you get proper drainage for your home and then making sure that you create a stable environment for supporting plant growth. Thus, you should start with bringing in as much fill dirt as it takes to create the grade you want. You then bring in enough topsoil to cover the fill dirt with several inches of rich, plant growth supporting soil. A contractor, like Southern Landscape Materials, can advise you on just how much fill dirt and topsoil you will need.