The WFS GetCapabilities request will return a document outlining:

• What operations (like GetFeature, Transaction, and LockFeature) the server support
• Where to send HTTP GET and POST requests
• A list of all the FeatureTypes (i.e. layers/datasets) the server has access to as well as:
  • what operations (Query, Insert, Update, Delete, Lock) are available for that FeatureType
  • the FeatureType name and namespace
  • what SRS/Projection the data is in
  • the spatial extents of the FeatureType
• what type of query functionality the server support