ESRI posted a pretty good explaination of all those new ArcGIS Server levels and what they mean.
ArcGIS Server is offered in a scalable line of editions (Advanced, Standard, and Basic) that are built from a common set of technology components. These editions are distinguished by their functionality.
- Advanced - ArcGIS Server Advanced is designed for GIS organizations that want to provide a central, server-based GIS for distributing GIS services across the organization or over the Internet. I provides spatial data management, visualization (both 2D and 3D), and spatial analysis capabilities.
- Standard - ArcGIS Server Standard is designed for GIS users who want to provide a central, server-based GIS for publishing geographic data as maps and globes. It provides spatial data management and visualization (both 2D and 3D) capabilities.
- Basic - ArcGIS Server Basic is designed for GIS users who want shared access to geographic data. It provides core geodatabase management tools and technology for data storage, management, and distribution (Web-based data replication).
Each ArcGIS Server edition is offered at an Enterprise level and a Workgroup level. These levels define each edition’s capacity.
Enterprise - The Enterprise level of ArcGIS Server supports an unlimited number of users via either direct connect or connection to an application server. It offers DBMS support for IBM DB2, IBM Informix, all editions of Microsoft SQL Server, and Oracle. It has no data or memory limits.
Workgroup - The Workgroup level of ArcGIS Server supports a maximum of 10 direct connect users. It includes an embedded DBMS (Microsoft SQL Server Express). It has a data limit of 4 GB and a memory limit of 1 GB.
So when ESRI says you are getting a copy of ArcGIS Server Standard Enterprise, you know now what that means.