STOMP
In plain terms
A simple text-based messaging protocol.
Going deeper
Streaming Text Oriented Messaging Protocol offers an easy, human-readable way for clients to talk to message brokers. Simplicity is its goal.
Under the hood
Text-based frames make it easy to implement across languages; less feature-rich than AMQP.
Examples
Message brokers, ActiveMQ, web messaging, simple pub/sub clients.
Think of it like...
Like a plain-text postcard format any messaging post office can understand.