Answer: Sometimes it is possible to purchase (at home centers or garden centers) dirt that has been packaged in plastic bags and labeled "topsoil". Sometimes a landscape supplier will sell "topsoil" by the cubic yard. There is no set definition for what "topsoil" is as a product.
In general terms, "topsoil" is the (usually thin) top-most layer of naturally organically rich soil, below which is found "subsoil". In different areas of the country the depths and characteristics of the soils can vary widely; the commercial material can vary widely, too.
I hope this answers your question.
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