The SAP tcode SEGW stands for:
Service Gateway Builder
SEGW is used to create and manage OData services in SAP NetWeaver Gateway. It provides a model-driven approach to build RESTful services that expose SAP data to external applications (like Fiori apps or third-party systems).
With SEGW, you can:
Define Entity Types and Entity Sets
Implement CRUD-Q operations
Map services to backend data models
Generate runtime artifacts for OData