Progressive Web Apps (PWAs) are web applications that are regular web pages or websites, but can appear to the user like traditional applications or native mobile applications.
Cloud Firestore is a flexible, scalable database for mobile, web, and server development from Firebase and Google Cloud Platform
You can write, read, listen to, and query the cached data. When the device comes back online, Cloud Firestore synchronizes any local changes made by your app to the data stored remotely in Cloud