What is the difference between Master, MSDB,TempDB and Model Databases?

Master Database: Records all the system-level information for an instance of SQL Server. It store all of the logins, linked servers, endpoints, and other system-wide configuration settings. The master database is also where SQL Server stores information about the other databases on this instance and the location of their files.

MSDB Database: Is used by SQL Server Agent for scheduling alerts and jobs.

TempDB Database: The tempdb system database is a global resource that is available to all users connected to the instance of SQL Server and is used to hold the following: Temporary user objects that are explicitly created, such as: global or local temporary tables, temporary stored procedures, table variables, or cursors.

Model Database: The model database is used as the template for all databases created on an instance of SQL Server. Because tempdb is created every time SQL Server is started, the model database must always exist on a SQL Server system.