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The star schema (sometimes called a star join schema) is the simplest 
data warehouse schema. In a star schema design there is a central fact table with a large number of tuples, optionally surrounded by a collection of dimension tables, each with a lesser number of tuples. Every dimension table participates in a 1::n join with the fact table.
A fact table is a table that represents quantitative or factual data. For example, in a business, a fact table might represent orders.
A fact table is often located at the center of a star schema or snowflake schema. It typically has a large number of tuples and is surrounded by a collection of dimension tables, each with a lesser number of tuples. The fact table participates in a join with every dimension table. In other words, a fact table can contain data but generally contains many join columns (with optional FOREIGN KEY constraints), each of which corresponds to the primary key column of a dimension table.
A dimension table (sometimes called a lookup or reference table) is one of a set of companion tables to a fact table in a star schema. It contains the PRIMARY KEY column corresponding to the join columns in fact tables. For example, a business might use a dimension table to contain item codes and descriptions.
Dimension tables can be connected to other dimension tables to form a hierarchy of dimensions in a snowflake schema.
The Retail Sales Example Database in the Quick Start is an example of a star schema.