A database is a collection of related data for various uses. There are three types of data models:
A Hierarchical data model organizes data into a tree-like structure that allows repeating information using defined parent/child relationships.
A Network data model is a flexible model representing objects and their relationships.
A Relational data model is a data model that stores information in the form of related two-dimensional tables.
A relational data model allows designers and users to identify relationships at the time the database is created or much later whenever new informational requirements from the data model are desired.
Hierarchical and network data models require relationships to be formed at the database creation, relational data models can be made up as needed.