A schema USUALLY represents the data structure illustration and relationships between different structures. A star schema constitutes a central fact table and different DIMENSION tables connected to it. The PRIMARY key of the dimension tables is a foreign key in the central fact table. 

This schema is called a star schema because the entity-relationship diagram can be visualized as a star whose points diverge from the central fact table as shown below:

The central fact table has two column sets- one set belongs to the fact table and the others are foreign keys to the dimension tables. Dimensions symbolize one or more attributes/hierarchies that categorize data. If there are no hierarchies, they are called lists or flat dimensions. The dimensional tables are smaller in size when compared to the fact table.

For EXAMPLE, The fact tables can store the entire sales INFORMATION and the dimension tables store data about clients, products, geographic regions, channels etc that are linked as foreign key references to the Sales information fact table.