File watcher 'Babel' is available for this file

I use webStorm for my meteor app developing, I changed javascript version under Languages & Frameworks > JavaScript to ECMAScript 6.
Now I get a green background label in the top of the screen saying:
"File watcher ‘Babel’ is available for this file. Description: ‘Transpiles ECMAScript 6 code to ECMAScript 5’ then gives 2 options [Add watcher Dismiss]

What should I do and why? and what will happens?