MOM is generally a higher-level concept used to describe architecture and overall design. Message-Oriented-Middleware-- very similar to EDA-- Event Driven Architecture.
Message Broker: Correct, this is the process that receives messages from producers and distributes them to consumers-- in other words brokering messages between applications.
AMQP: Is a wire protocol that is used by the broker and clients to agree on how to send messages between each other and support various features-- timestamps, expiration, transactions, etc.
JMS: Is a Java API standard for applications and brokers to adhere to. It is a thin API-only specification and not a wire protocol. JMS-compatible brokers, such as ActiveMQ, IBM MQ, etc. implement wire protocols that support the JMS API specification.
To put it all together:
An organization may adopt a Message Oriented Middleware (MOM) in order to decouple applications at runtime. This architecture will be achieved by using JMS-compatible message brokers and JMS-compatible clients that are communicating under the covers using the AMQP wire protocol.