It uses firebase storage for storing multimedia images and firestore for user information in key-value pair.

FireBase Storage
Firebase Cloud Storage is a feature-rich object storage service for the development of applications. It is a cost-friendly service that assigns Google-level security for the download and upload of files. Cloud Storage can help users store user-generated content and media files.

Firebase Cloud Firestore
Google Firestore or Cloud Firestore is a part of the Google Firebase app development platform. It is a cloud-hosted NoSQL database option for the storage and synchronization of data. Users can directly access Firestore from their web and mobile applications with native SDKs.

This app uses storage and firestore in combination to store different superhero characters data.