SQS equivalent in Azure is not Service Bus. It's Azure Storage Queues. Or ASQ for a shorter name. That's the short answer.
SQS is a simple queue service. So is ASQ. They exhibit very similar attributes. Both are HTTP based, small payload, almost no compute-based features, not intended for enterprise service bus but rather task-based communication, pub/sub is not provided out of the box and usually requires an additional service (SNS for SQS and EventGrid for ASQ). While SQS has been slightly upgraded (FIFO queues, some support for headers, etc.) this is mostly was done to compensate for the fact that there was no enterprise messaging service offered by AWS. Now there is one, AmazonMQ/ActiveMQ.
what would be the main difference between service bus and SQS
A few key differences are:
- SQS is a queuing service; ASB is a messaging service
- SQS has almost no compute based features; ASB offers a lot of advanced features
- SQS offers no native pub/sub feature and requires SNS; ASB supports pub/sub natively
- SQS doesn't provide a dedicated tier; ASB does (Premium tier)
- SQS has a limited message size (256KB); ASB (Premium) supports up to 1MB today with 100MB later this summer
and a few more that I'm probably missing out for now, but this should suffice.