On Your Lot Builder
An ‘on your lot builder’ (or ‘build on your land builder’) is a builder who constructs your customized home on your land. The builder does not own the land and has not invested resources into development of the property. Suprema Homes is an ‘on your lot builder’.
Spec Builder
On the other hand, a spec home builder or ‘speculative home builder’, purchases land, develops the property, and builds the home, speculating that the home will sell quickly and easily. Sometimes spec home builders will allow a few changes to the home if sold before completion.
Of course there are other types of builders and many variations, each specializing in their own category.