Enterprise License
ArcGIS for Server Enterprise allows simultaneous operation of multiple machines, supporting the multi-user databases for GIS services management in the organizations.

The main characteristics of the license include:
•    Maintenance of many simultaneous operations of multi-user geodatabases.
•    Virtual storage of unlimited GIS data in a multi-user geodatabase.
•    Enhancing the capabilities of the components of ArcGIS for Server among multiple machines.

Workgroup license
ArcGIS for Server Workgroup is designed to support medium to small projects and departments. It has many of the capabilities of the Enterprise License but can be installed on only one machine.

With ArcGIS for Server Workgroup you can:
•    Maintain 10 simultaneous connections to a multi-user geodatabase
•    Store up to 10 GB GIS data in multi-user geodatabase