Types of databases
All the persistent data from an application should live in a database. As we've discussed, data is the most critical aspect of any application, and proper handling of it is critical to ensure the viability of the project.
Technically, databases are collections of data themselves and are handled by the database management system (DBMS), the software that allows the input and output of data. Normally, the word "database" is used for both the collection and the management system, depending on the context. Most DBMSes will allow access to multiple databases of the same kind, without being able to cross data between them, to allow logical separation of the data.
Databases have been a critical tool for most of the time software systems have been available. They create an abstraction layer that allows accessing data without having to worry too much about how the data is structured by the hardware. Most databases allow the structure of...