Server Name uniquely identifies a database connection.
For Crystal Report connection types, Server Name must match the name of the data source in the Crystal Report. For example, if your report was created from a DSN called AccountingProduction then the server name must be AccountingProduction. If your report connects directly to the data source the server name will be the PC computer name for the data source.
For Dynamic Pick List connection types, Server Name is the name of the server you are attempting to connect to. For example, if you have SQL Server running on a machine called DBPROD, use this for the server name.
For Advanced Pick List connection types, Server Name is just an identifier and you can put anything you want here.