Re-add a useful section

Author: gaearon

content/docs/create-a-new-react-app.md

@@ -74,10 +74,18 @@ The following toolchains offer more flexiblity and choice. We recommend them to
 
 - **[nwb](https://github.com/insin/nwb)** is particularly great for [publishing React components for npm](https://github.com/insin/nwb/blob/master/docs/guides/ReactComponents.md#developing-react-components-and-libraries-with-nwb). It [can be used](https://github.com/insin/nwb/blob/master/docs/guides/ReactApps.md#developing-react-apps-with-nwb) for creating React apps, too. 
 
-- **[Parcel](https://github.com/parcel-bundler/parcel/)** is a very fast JavaScript bundler that requires no configuration.
+- **[Parcel](https://parceljs.org/)** is a very fast JavaScript bundler that requires no configuration.
 
 - **[Razzle](https://github.com/jaredpalmer/razzle)** is a server-rendering framework that doesn't require any configuration, but offers more flexibility than Next.js.
 
 ## Creating a Toolchain from Scratch
 
+A JavaScript build toolchain typically consists of:
+
+* A **package manager**, such as [Yarn](https://yarnpkg.com/) or [npm](https://www.npmjs.com/). It lets you take advantage of a vast ecosystem of third-party packages, and easily install or update them.
+
+* A **bundler**, such as [webpack](https://webpack.js.org/) or [Parcel](https://parceljs.org/). It lets you write modular code and bundle it together into small packages to optimize load time.
+
+* A **compiler** such as [Babel](http://babeljs.io/). It lets you write modern JavaScript code that still works in older browsers.
+
 If you prefer to set up your own JavaScript toolchain from scratch, [check out this guide](https://blog.usejournal.com/creating-a-react-app-from-scratch-f3c693b84658) that re-creates some of the Create React App functionality.