## 1.1. What is a database?

You can define a database as a collection of data on one topic. It is organised in a way allowing to easily browse the information, make changes or add new items.

Look at this diagram for one of the above examples: a simple phone book.
A diagram of a phone number database
The above picture shows a set of two contacts each of which is presented on a separate card. It appears that such a card can constitute a single line in a table:

Contacts
Name | Tel No.
Joan | 699 23 43 12
Adam | 711 19 77 21

Terms and definitions: A single data which constitutes a part of a greater collection can be called a line or more professionally a record. The collection is narmally called a table. Moreover, the most natural name for the table is one describing the data it offers/stores which is Contacts. Furthermore, each line in the table consists of columns often also called fields. In the table Contacts there are two columns (fields): Name and Tel No..

For simple uses a single table can make up a database. Many people consider these two equivalent. As you will see, for real databases we usually need more than one table.

To sum up, you have already got a simple database with one table Contacts.