What is ActiveMQ used for - can we apply messaging concept using a Database?

Question

I looked it up and it used to send messages between 2 systems.
But why? Why wouldn\'t you just use a Database?
There must be some feature that ActiveM

Answer 1

With RDBMS, when you process a row of data, you typically update a flag indicating that the row has been processed so that the processing is not repeated.

However, with Message Queue, you only have to acknowledge a message and the next consumer will process the next one.

The difference is that the UPDATE statment in a RDBMS is a really slow operation compared to the acknowledge in activmeq.