JSON is one of the most widely used data interchange formats. It is used as a storing format in several NoSQL solutions, in particular, in Microsoft Azure DocumentDB. In my opinion, today JSON is yet more popular than XML. One of the reasons of its popularity is more simple form and better readability in comparison with XML. Naturally, there was a long-standing need in having an option to process data in this format within SQL Server. In SQL Server 2016, this option has been established.
First of all, it is worth mentioning that there is no separate type for storing JSON, unlike XML. That is why, JSON is stored in the standard variables, or in the varchar or nvarchar fields.