TypeScript 2.1 isn't a major update but it does bring in some enhancements in the form of a smarter interface, downlevel async functions as well as object rest and spread. According to Microsoft:
"This release comes with features that we think will drastically reduce the friction of starting new projects, make the type-checker much more powerful, and give you the tools to write much more expressive code."
You can get more information from this Microsoft blog post which details how these new features work. Developers can start using TypeScript by installing it through the npm packet manager through Node.js or by downloading the TypeScript 2.1 installer for Visual Studio 2015 after getting Update 3.