The land-use plan narrows the definitions of the zoning plan (see "What is a land-use plan?"), and contains legally binding specification about the permitted types and dimensions of constructions within a part of a towns territory. Possible contents are defined in the Baugesetzbuch.
Unlike the zoning plan, land-use plans do not have to be designed for the entirety of the surface of a town's territory. Land-use plans are legally binding, which means that they count as a communal statute. As such, they determine the bounds and limitations of land property and real estate within a town.
It's up the the communal administration to decide whether a land-use plan should be created. They must only do so "as soon as they become nesessary for the urban development and order" (§ 1 (3) BauGB). Otherwise, the town is not compelled to create those plans, and they usually are only devised for a part of the town's territory.