The WebSocket Protocol is already built into modern browsers and provides bidirectional, low-latency message-based communication. However, as such, WebSocket it is quite low-level and only provides raw messaging.
This is where The WebSocket Application Messaging Protocol (WAMP) enters. WAMP adds the higher level messaging patterns of RPC and PubSub to WebSocket - within one protocol.
Technically, WAMP is an officially registered WebSocket subprotocol (runs on top of WebSocket) that uses JSON as message serialization format.
WAMP embraces open Web standards and was designed to be easy to use and simple to implement.