A database is simply an organized collection of information in which descriptions about the information have been systematically entered. These descriptions, called records, can be easily searched. Database users can retrieve records about the information—and often the information itself—based upon search terms. Additionally, database managers can continually add, edit, and/or remove the database content as well as the content records.
In libraries, the term database has come to have a secondary meaning--a proprietary database to which the library subscribes for the use of its users.
For a short, but more indepth, overview of databases, check out this 4 minute video.
You can also go to an alphabetical listing of all the databases offered by STLCC Libraries.