I wonder what is the difference between them. Are they describing the same thing?
Is Google App Engine Service Task Queue is an implementation of Message Queue?
GAE's Task Queues are a means for allowing an application to do background processing, and they are not going to serve the same purpose as a Message Queue. They are very different things that serve different functions.
A Message Queue is a mechanism for sharing information, between processes, threads, systems.
An AppEngine task Queue is a way for an AppEngine application to say to itself, I need to do this, but I am going to do it later, outside of the context of a client request.