I'm wondering the idea behind this as I don't understand which kind of situation you will use this.
More info here.
React is a programming technology created by Facebook that provides a cross-platform interface for creating applications. A specific extension of React, called forcereact, is an implementation that provides Salesforce-specific features, and is part of the Mobile SDK. You'll want to start from this trail, which gives you a quick crash course in forcereact, as well as links to an example application, documentation, and so on.