A database is a place where information or data can be stored until it is removed or replaced. Facebook uses a database to store usernames and corresponding passwords. Android devices have internal databases that store information about you or your phone. App Inventor allows us to access this database through the use of TinyDB.
App Inventor makes it easy to store data through its TinyDB and TinyWebDB components. Data is always stored as a tag-value pair, with the tag identifying the data for later retrieval. TinyDB should be used when it is appropriate to store data directly on the device. When data needs to be shared across phones (e.g., for a multiplayer game or a voting app), you’ll need to use TinyWebDB instead. TinyWebDB is more complicated because you need to set up a callback procedure (the GotValue event handler), as well as a web database service.
To create your own web service, follow the instructions on the TinyWebDB component page.