To send message to GCM Pushwoosh uses GCM protocol. That's pretty much POST JSON message over HTTP protocol: http://developer.android.com/google/gcm/notifications.html
When sending message to Pushwoosh via Remote API you again POST JSON message over HTTP protocol: http://www.pushwoosh.com/programming-push-notification/pushwoosh-push-notification-remote-api/
HTTP protocol: http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol
JSON: http://en.wikipedia.org/wiki/JSON
I hope it helps!