Difference of Azure Deployment Environments and Azure DevTest Lab

Hi Guys,

for me sometimes, the number of Azure Services, is overwhelming. What is really annoying is that you can't find two lines of description, which explains the concrete uses cases for the different Azure Service.

So does someone know the difference between Azure Deployment Environments and Azure DevTest Lab? Does someone have concrete use cases for this two Azure Services?

Cheers,
Chico