What is the difference between a MessageListener and a Consumer in JMS?

Question

I am new to JMS. As far as I understood Consumers are capable of picking messages from queue/topic. So why do you need a MessageList

Answer 1

from the docs:

For synchronous receipt, a client can request the next message from a message consumer using one of its receive methods.

For asynchronous delivery, a client can register a MessageListener object with a message consumer.