So, TFS/VSTS is a suite of developer services. They fully support and integrate with git. In other words, git is a first-class citizen in TFS/VSTS. The centralized version control system in TFS/VSTS is called "Team Foundation Version Control" or TFVC.

There were a bunch of drivers to move to git: 1. DVCS has some great workflows. Local branching, transitive merging, offline commit, etc. 2. Git is becoming the industry standard and using that for our VC is both a recruiting and productivity advantage for us. 3. Git (and it's workflow) helps foster a better sense of sharing which is something we want to promote within the company. There are more but those are the major ones.

Good questions. TFS is a whole suite of services: 2 version control systems (TFVC and Git), work item tracking, build orchestration, package management, and more. VSTS is the roughly-analogous cloud-hosted version.

I'd have to dig up the link: a few years ago our VP had a good blog post on why we chose to add a Git server to our offering. TFVC is a classic centralized version control system. When we wanted to add a distributed version control, we looked at rolling our own but ultimately concluded that it was better to adopt the de facto standard.