The databases are usually bins for saving everything (data) seized into a few real files which has been manipulated by special interpreter with own commands. It also represents next layer into which must data go. It's good in case of more entries and especially with searching in it. For us it's mainly SQL databases MySQL (MariaDB) and PostgreSQL. Page owners found them most time. In these databases are data in files represents and accessing like tables. For details look onto their own documentation.
As I says, I wrote this system works without databases. Only data source is file system. But is also possible to hack system for using databases.
For this system I wrote only two things - Pedigree and connection (database) (both now private - installation process). These modules needs SQL type database. If you once use database, remember that databases needs more complex configuration and their modules prepared structures as tables.