A database is a collection of related data.
Our mobile phones have a contact book which contains names and contact numbers. Here name and their corresponding contact numbers are examples of related data. And the entire contact book is an example of a database.
Every database is designed, built, and populated with data for a specific purpose.
The contact book is designed for a specific purpose, i.e. for providing contacts and addresses of people at time of need.
A database can be of any size and complexity.
The address book may be of hundred entries or of thousand entries. A simple address book may contain fields like name and phone number, while a complex address book may contain name, phone number, address, e-mail, note, etc.
A database may be generated and maintained manually, or it may be computerized.
The address books were previously maintained in a diary or notebook. This was a manual process. Nowadays, we maintain records digitally say in form of excel files or MS-Access. This is the computerized form of database.