Flutter is an open source framework that is created by Google for mobile application development. Using this framework, apps can be developed for both Android and iOS Devices.
Firebase is a platform developed by Google for creating mobile and web applications. It is a Backend-as-a-Service — BaaS and is used widely for creating realtime mobile applications. Firebase is your server, your API and your database, all written so generically that you can modify it to suit most needs.
The product comes with a complete setup guide which will guide you through everything from setting up the local environment to configuring firebase.
It is absolutely easy to set up the app and firebase in a few easy steps.