Recently, on colleagues's advice, I found myself trying out this tool called RabbitMQ(https://www.rabbitmq.com/),
A "message broker" that manages and transmits messages between a client and a server that is usually used to manage "queues" of operations to be performed (an example could be the massive sending of emails).

To put it simple there is a "Publisher" that sends data to a "Consumer"

Publisher

this is an php's example of a publisher , it will send Hello world in the "hello" channel

Consumer

this is an php's example of a consumer , it will receive messages from the hello channel and then when it's called it will send the message in the $callback function

Trying it out I realised the great potential it has as a tool for managing "heavy" operations that can be run in parallel without blocking the main thread (especially for applications) such as video processing, image and video optimisation, emailing and many other applications.
Do you use it? If yes, for what?
From what I've been told it is also widely used in microservice structured systems to connect them.