Azure DevOps CLI is an extension on top of Azure CLI and it's cross platform as well. Why we need to use Azure DevOps CLI as we already have REST APIs available to interact with Azure DevOps.
Live Interaction
You already using Azure CLI to connect to your azure subscription and also to run your GIT commands etc..so without getting out of that context you can interact with Azure DevOps under that subscription. So it's a live interaction with your Azure and Azure DevOps Pipelines in a same command prompt window.
Automation
You need scripts to define your Azure DevOps Projects Pipeline setup, which will run for each new pipeline occurrences to maintain your common organizational standards across. Azure DevOps CLI supports to define customized scripts here.
How to Install
Make sure that you have latest Azure CLI already installed. Then just use below command to add Azure DevOps CLI.
See Commands
You can see 1st level of commands as below.
Seek Help for Commands
Below we asked help for an high level command (pipelines) and also asked help for it's sub command (create) as well.
Now use the URI of your Azure DevOps organization and have a sample project in GIT. Then try to run Azure DevOps CLI commands to manage your pipeline.