GeoServer serves data using standard protocols established by the Open Geospatial Consortium:
The Web Map Service (WMS) supports requests for map images (and other formats) generated from geographical data.
The Web Feature Service (WFS) supports requests for geographical feature data (with vector geometry and attributes).
The Web Coverage Service (WCS) supports requests for coverage data (rasters).
These services are the primary way that GeoServer supplies geospatial information.