Let us start with Databases. A simplistic view of Databases is that it stores data which can be read, updated and deleted at a later time. This data can represent multiple things depending on the application using it and the data itself can be stored in multiple ways as well. For example your application can serialize the objects and store them, save the object state and values in a xml file or some other format. One format that really took off was Relational Databases, where you store the data explicitly in tables and some information about it implicitly through relation between those tables.
