A dimension table, such as a Product dimension, is a container for relational tables. Each dimension table contains data related to facts in the fact table.
When a dimension table joins to the fact table, that dimension table and other dimension tables joined to it form a dimension. A dimension in an OLAP model represents a dimension (or characteristic from a data warehouse) you want to report in Essbase. See Multidimensional Databases.
When you create a dimension in an OLAP model, the dimension becomes available for use in creating a dimension in an associated metaoutline. You can drag a predefined OLAP model dimension directly into the metaoutline to create a dimension. The newly created metaoutline dimension then becomes a dimension in the Essbase database that you create when you perform a member or data load.
If your source is a relational database, when you build a metaoutline, you can create user-defined dimensions that do not exist in the associated OLAP model.