System Landscape Selection
The SAP NetWeaver Administrator is a Web-based tool for managing and monitoring SAP NetWeaver. There are two main scenarios for using this tool:

The local scenario applies to developer installations as well as to very small customer landscapes. The tool is part of every SAP NetWeaver installation and can be used to manage the local system the tool is running on.
In the central scenario, the same tool as in the local scenario is used to manage the entire system landscape. In this case, the tool is closely integrated with other parts of the central management infrastructure. The System Landscape Directory (SLD) is used to obtain data about the system landscape, the Computing Center Management System (CCMS) provides the monitoring data visualized by the Web Admin.
At SAP NetWeaver Administrator startup, you can choose which of the above two scenarios you want to use.
More information: Defining System Selections.