What does => mean in javascript

Question

I'm really confused about what this '=>' symbol is doing in a basic node.js tutorial that I just try to learn to.

This is the used of the syntax:

http.createServer((req,res)=>{
  res.writeHead(200, {'Content-type':'text/html'});
  res.end('<h1>Hello NodeJS</h1>');
})

I'm a php developer and really want to try Node.js, just stuck and curious about this specific symbol mean and I try to google it but failed.