Update README.md

Closes #215

Author: pensierinmusica

README.md

@@ -17,12 +17,23 @@ It transforms CSS specs into more compatible CSS so you don’t need to wait for
 
 ## Why **postcss-cssnext** ? What is the difference with **cssnext** ?
 
+### Short answer
+
+If you're using PostCSS in your build process, and want to add cssnext, you need only `postcss-cssnext`
+(check the "options" section here below).
+Otherwise, if you like cssnext to work as a full standalone package with its own cli
+(independently of PostCSS), use `cssnext`.
+
+### More details
+
 cssnext was at first designed to be a complete tool, before PostCSS became
 popular; thus, includes some options that don't really belong in a PostCSS
 plugin (e.g., `import`, `url`, `compress`, `plugins`).
 These days, most people use PostCSS directly so we decided to make integration of
 cssnext more simple by providing a simple (real) plugin.
 
+### Options
+
 If you were using cssnext with some options here is what you need to know:
 
 - `import`: just add into your plugins list