What's the principal difference between MS App

I am "a bit" confused in understanding of what of those two services are capable for and what are the core differences between of them.

In general, I understand what they provide, and separately I used them both earlier (VSTS as issue tracker, mostly), and AppCenter for the sources to be built and deployed.

However:

1. They both have building and (apparently) publishing capabilities.

In DevOps has the option of setting up the Pipeline:

Same way as AppCenter has mostly the same:

2. They both also have Tests sections with (seems like) similar functionality.

3. They both provide ability of deploying the build into Play/App Stores.

AppCenter - with "Stores" section, and DevOps with this plugin (at least).

They both also have some specific features (like AppCenter has PushNotifications functionality and Azure DevOps has issue tracking), however, for the apps distribution they look pretty alike.

So, which of them should be used for what particular tasks? Or this is just one the modern "marketing" feature of Microsoft, when there is mostly no difference, but those are just two similar thing wrapped with different-colored envelope?

In short, App Center is for mobile app deployment & monitoring whereas DevOps is for any-platform development & deployment. App Center focuses on deploying and monitoring mobile apps, while DevOps focuses on the entire development lifecycle of all types of projects along with deployment.

So I think one needs both for an entire project perspective: DevOps to develop and deploy, and App Center to deploy and/or monitor.

If we are comfortable with multiple tools like github/bitbucket for git, jira or trello for management, then we only need to have App Center. Otherwise everything can be under one roof with DevOps.

Anyhow, I prefer App Center for my projects as I can have all the features of bitbucket and jira, along with an easier test & deployment set up and monitoring.

I can't say they should merge everything under DevOps, as there are users like me who prefers to use only the deployment and/or monitoring (of mobile apps) with Microsoft and enjoy other products for the rest. Hence, with the current set up, they are addressing two different sets of customers.