Update README.md

Author: petehunt

README.md

@@ -89,7 +89,9 @@ This is a fairly crazy idea for a number of reasons. It makes media queries more
 
 ## Learning server rendering
 
-Server rendering is often called "universal" or "isomorphic" JS. It means that you can take your React components and render them to static HTML on the server. You need server rendering if you notice that your initial render is too slow (because the browser needs to download a bunch of JavaScript) or if you want to improve your search engine ranking (while it's true that Google now indexes client-rendered content, as of January 2016 every time it's been measured it's been shown to negatively affect ranking, potentially because of initial render performance).
+Server rendering is often called "universal" or "isomorphic" JS. It means that you can take your React components and render them to static HTML on the server. This improves initial startup perormance because the user does not need to wait for JS to download in order to see the initial UI, and React can re-use the server-rendered HTML so it doesn't need to generate it client-side.
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+You need server rendering if you notice that your initial render is too slow or if you want to improve your search engine ranking. Wwhile it's true that Google now indexes client-rendered content, as of January 2016 every time it's been measured it's been shown to negatively affect ranking, potentially because of the performance penalty of client-side rendering.
 
 Server rendering still requires a lot of tooling to get right. Since it transparently supports React components written without server rendering in mind, you should build your app first and worry about server rendering later. You won't need to rewrite all of your components to support it.