What are the possible use cases for Amazon SQS or any Queue Service?

So I have been trying to get my hands on Amazon's AWS since my company's whole infrastructure is based of it.

One component I have never been able to understand properly is the Queue Service, I have searched Google quite a bit but I haven't been able to get a satisfactory answer. I think a Cron job and Queue Service are quite similar somewhat, correct me if I am wrong.

So what exactly SQS does? As far as I understand, it stores simple messages to be used by other components in AWS to do tasks & you can send messages to do that.

In this question, Can someone explain to me what Amazon Web Services components are used in a normal web service?; the answer mentioned they used SQS to queue tasks they want performed asynchronously. Why not just give a message back to the user & do the processing later on? Why wait for SQS to do its stuff?

Also, let's just say I have a web app which allows user to schedule some daily tasks, how would SQS would fit in that?