A database is a collection of data, data tables, and other objects that are organized and presented to serve a specific purpose, such as facilitation of searching, sorting, and recombination of data. Databases are stored on devices.
A device is an operating-system file in which databases are stored. One database can be stored on several devices. SQL Server has two types of devices: database devices, which store databases, and dump devices, which store backups of a database.
When SQL Server is installed, the setup program creates the MASTER, MSDBDATA, and MSDBLOG database devices. It creates the master, model, tempdb, and pubs databases and places them on the MASTER database device. It creates the msdb database and places it on the MSDBDATA database device, and places the msdb transaction log on the MSDBLOG device.
In most cases, it is best if the devices created by setup are not being used for other databases. Before users create databases, they should create one or more other devices for the use of those databases.
For information about the system databases installed by the setup program, choose one of the following topics: