Subdivision is the process of splitting a piece of property into any number of smaller tracts of land within the original tract. Subdivisions vary from a simple one-lot subdivision where, for example, lets say a parent would like to split off a tract of land for a son or daughter, to very complex 100-lot residential development. Lot Addition is the process of combining lots or adding land to an existing property.

Subdivisions are required to go through an approval process with your local supervisors or planning commission, or both.
The approval requirements vary from municipality to municipality. Also, depending on the size and complexity of the subdivision, it may also be required to go through an approval process with the county planning office.