Enterprise Services Repository
Developers use the Enterprise Services Repository (ES Repository) to model and specify objects that are to be implemented later at various levels of detail. You use the Enterprise Services Builder (ES Builder) to access the objects in the ES Repository.
The ES Repository is used in various SAP NetWeaver IT scenarios:
● Enabling Enterprise Services
● Enabling Application-to-Application Processes
● Enabling Business-to-Business Processes
The Enterprise Services Repository section describes the corresponding tools in detail. Scenario-specific procedures are described in the role-specific guides. The ES Repository is mainly used by developers. Service and also interface development is a central topic, irrespective of the IT scenario. However, the detailed procedures do differ depending on the IT scenario.
More information: Introduction to Service Development
Software component
versions are the smallest shipment units that can be delivered using the
objects of the ES Repository. To be able to develop within a software
component version that is relevant for shipment, it must be maintained in the
software catalog of the
System Landscape
Directory (SLD). SAP products and the corresponding software component
versions are already maintained in the SLD. You can also enter external
products, software components, and software component versions in the SLD
(see:
Software
Catalog).

In addition to the shipment-relevant software component versions, you can also work with a local software component version in the ES Repository initially; this does not have to be maintained in the SLD.
...
1. Begin by modeling your application in the ES Repository.
More information: Defining Design Objects for Modeling Applications
2. In the subsequent step, specify in detail the design objects your application requires.
More information: Defining Design Objects for Specifying Applications
3. Continue with the implementation and configuration of your application.