JMS - Java Messaging Service as defined by JSR-914 or JSR-3431.
Message/JMS Message - An object that contains the data being transferred between clients JMS.
Producer/JMS Producer/Publisher - A JMS client that creates and sends messages.
Queue/JMS Queue - A staging area that contains messages that have been sent and are waiting to be read (by only one consumer). Contrary to what the name queue suggests, messages don't have to be received in the order in which they were sent. A JMS queue only guarantees that each message is processed only once.
Topic/JMS Topic - A distribution mechanism for publishing messages that are delivered to multiple subscribers JMS.