Categories are the main organizational structure for families within Revit. Think of categories as high-level classifications of elements you find inside buildings. Categories include walls, windows, doors, ducts, pipes, structural framing, structural columns, to name a few.

The 3 kinds of families in Revit are: system families, loadable families, and in-place families. Most elements that you create in your projects are system families or loadable families. Loadable families can be combined to create nested and shared families.

The three kinds of Revit families are system families, loadable families, and in-place families. Within a family, you can create multiple types for different sizes, materials, or any other parameter you want to change. while keeping the material and hardware the same for each type.