title: Difference between FCM (Firebase cloud messaging) and GCM? Which one is better for Android push notification?
body: <p>I want to use Push notification in my app, Other things like sync with server database I had handled manually , So which is the best option to go ahead?</p>
  
  <p>Also can I use GCM API keys with FCM? </p>
  
  <p>Does FCM is free for unlimited number of messages? </p>