Before you start creating databases on a SQL Server 2014 instance, you should have a good understanding of the system databases that are installed by default when a SQL Server 2014 instance is created. Each SQL Server 2014 system database has a specific purpose and is required to run SQL Server. So, having a good understanding of the SQL Server system databases is useful when you are troubleshooting SQL Server issues.
By default, when you install a SQL Server 2014 instance, the SQL Server 2014 setup program creates the following five system databases: master, model, msdb, tempdb, and resource. Apart from these system databases, there is another system database called distribution that does not exist until you configure replication on the SQL Server instance.