Microsoft Visual Studio is a programming tool that can provide an environment for either individual developrs or a group of developers to create apps individually, or collaboratively as a team.
Products available in the Microsoft Visual Studio range
This program provides an environment for individuals or groups to develop their own apps for Windows, SharePoint, web/cloud and mobile devices. Visual Studio Professional supports all the major programming languages such as Visual Basic and C++ to name a few. Lastly, its MSDN subscription would provide organizations a server license for the Team Foundation server and one CAL.
The Team Foundation Server works as a project management server that can allow groups of developers to collaborate effectively on one or more projects. Some of its notable features include the ability to manage multiple versions of their app, track events that lead to a bug and also increased accessibility through a web-based Visual Studio that can be accessed through a browser.
Client Access Licenses, or CALs, authorizes users or devices to access the services of the Visual Studio Team Foundation server. Device CALs authorizes one computer or device regardless of the number of users, while on the other hand, User CALs authorizes specific users regardless of the device they're using.