One of Drupal's features is that it allows database prefixes, so people can host more than one site in a single database, or share the database with other application programs.
As a site grows, people find the need to separate those sites into their own databases, making the prefix unnecessary.
To do that, the following steps are needed:
Backup the existing database
In order to start this process, you have to perform a dump of the database. This is needed for two purposes, one is to have a backup of all your data, and the second is to be able to copy it to the other database, which may be on another host altogether.