What is Azure Cloud Shell?
AZCLI Is an embedded terminal which is can be used within your browser, or even the Azure Mobile app. The Azure Cloud Shell enables you to easily use both Bash and PowerShell directly in the browser or Azure Mobile app.

It is really an Amazing tool, easy to use and execute whatever we need. Managed by Microsoft with no cost!

What is DevOps?

DevOps is the union of people, process, and products to enable continuous delivery of value to our customers. DevOps is a methodology or a practice that brings together development (Dev) and operations (Ops) teams for deploying efficient applications while shortening the development life cycle overall.

Azure Dev/Test Labs provides developers and testers a self-service sandbox environment to quickly create Dev/Test environments while minimizing waste and controlling costs

Actually, there are many ways to use Azure for Testing and development purposes one of them is to use Visual studio subscription which it will gave you 12 months of free use with 150$ monthly for free! but for organization which they want to deploy a testing/development environments on azure and to apply some kind of automation on these resources azure provide us a way to achieve that thru Azure Dev/Test.