WMS
OpenGIS® Web Map Service Interface Standard (WMS) provides a simple HTTP interface for requesting geo-registered map images from one or more distributed geospatial databases.
WFS
OpenGIS® Web Features Service Interface Standard (WFS) provides an interface allowing requests for geographical features across the web using platform-independent calls.
REST
REST (Representational State Transfer) API Map Service resource provides basic information about the map, including the layers, spatial reference, initial and full extents, map units, metadata, and copyright text.