What is a database? In real meaning a database is nothing more than gathering of information that exists over a long phase of time, often many years. In common manner of speaking, the term database refers to a compilation of data that is managed by a DBMS. The DBMS is expected to:

1. Allow users to build new databases and identify their diagram (logical structure of the data), using a specific language called a data-definition language.

2. Provide users the capability to query the data (a "query" is database language for a question about the data) and change the data, using proper language, often called a query language or data-manipulation language.

3. Support the storage of very huge amounts of data - many gigabytes or more - over a long phase of time, keeping it safe from mishap or illegal use and allowing well-organized right to use the data for queries and database modifications.

4. Control access to data from many users at once, without allowing the actions of one user to influence other users and without allowing instantaneous accesses to damage the data by accident.