The Server Processes lists the processes relevant to SQL Server. These can be internal processes, or external ones, at client stations.
The Server Processes screen
For example, in the above screen, all processes except process "51" are server side internal processes, and process "51" is Database Workbench, connected to make a screenshot of this screen. The Application column lists the application that's connected to SQL Server - this can be very useful when troubleshooting a particular application or workstation.
Some of the available processes in the list can be killed using the Kill Process button or the menu option from the context menu.
The Server Processes screen automatically refreshes the list every n seconds, where n can be adjusted using the spin edit box on the top right of the screen - this refreshing can be paused by checking the Paused checkbox and can be forced by using the Refresh button on the top left of the screen.