Generate API Key And FCM Sender Id

Google API Key is a way via which you can monitor your application’s API usage in the Google API Console. Registering for an API Key makes certain that Google can contact you about your application. This blog gives you detail how to create Google API Key for Standard user. So, if you are using API under standard plan, then in a project of your choice the API Key set up needs to be done.
Firebase Cloud Messaging (FCM) is used to deliver push notifications to Android devices, Google Chrome and Mozilla web browsers. With FCM credentials you can set up Web Push Notification service in your site.The API key is stored securely and used by the Push Notifications service to connect to the FCM server and the sender ID (project number) is used by the Android SDK and JS SDK for Google Chrome and Mozilla Firefox on the client side.
Here is a tutorial that describes you to generate API Key and FCM Sender Id step by step.