The model is centered on two types of entities, facts and dimensions. Facts are entities that deal with measurements or indicators. A fact entity for a sales organization could measure revenue per month, or units sold per day. A fact for a manufacturing organization could measure defects per lot per day or units produced per week. Dimensions are entities that represent dimensional information about the facts.
Dimensions are ways that the data can be sliced or viewed or segmented.
Dimensions typically represent and n-leveled hierarchy such as a product hierarchy or sales organization hierarchy. In a dimensional model, this is one entity. The same is true for a product dimension. The product dimension can represent SKU, its brand, the brand's category, the category's division. Although the dimensional model is a useful approach for modeling the data needed to create a database for data warehouses and quick queries, there are shortcomings.