RabbitMQ supports several messing protocols, directly and through the use of plugins. This page describes the supported protocols and helps differentiate between them.
RabbitMQ was originally developed to support AMQP. As such this protocol is the "core" protocol supported by the broker. All of these variants are fairly similar to each other, with later versions tidying up unclear or unhelpful parts of earlier versions. We have extended AMQP 0-9-1 in various ways.
AMQP 0-9-1 is a binary protocol, and defines quite strong messaging semantics. For clients it's a reasonably easy protocol to implement, and as such there are a large number of implementations available for many different programming languages and environments.
If you are just looking to use RabbitMQ, we recommend using AMQP 0-9-1.
STOMP is a text-based messaging protocol emphasising (protocol) simplicity. It defines little in the way of messaging semantics, but is easy to implement and very easy to implement partially (it's the only protocol that can be used by hand over telnet).
RabbitMQ supports STOMP (all current versions) via a plugin.
MQTT is a binary protocol emphasising lightweight publish / subscribe messaging, targetted towards clients in constrained devices. It has well defined messaging semantics for publish / subscribe, but not for other messaging idioms.
RabbitMQ supports MQTT 3.1 via a plugin.
Despite the name, AMQP 1.0 is a radically different protocol from AMQP 0-9-1 / 0-9 / 0-8, sharing essentially nothing at the wire level. AMQP 1.0 imposes far fewer semantic requirements; it is therefore easier to add support for AMQP 1.0 to existing brokers. The protocol is substantially more complex than AMQP 0-9-1, and there are fewer client implementations.
RabbitMQ supports AMQP 1.0 via a plugin.
HTTP is of course not a messaging protocol. However, RabbitMQ can transmit messages over HTTP in three ways: