A family is a group of elements with a common set of properties, called parameters, and a related graphical representation.
Different elements belonging to a family may have different values for some or all of their parameters, but the set of parameters (their names and meanings) is the same. These variations within the family are called family types or types.
For example, the Furniture category includes families and family types that you can use to create different pieces of furniture, like desks, chairs, and cabinets.
Although these families serve different purposes and are composed of different materials, they have a related use. Each type in the family has a related graphical representation and an identical set of parameters, called the family type parameters.
When you create an element in a project with a specific family and family type, you create an instance of the element. Each element instance has a set of properties, in which you can change some element parameters independent of the family type parameters. These changes apply only to the instance of the element, the single element in the project. If you make any changes to the family type parameters, the changes apply to all element instances that you created with that type.