1. What is a database?

A database is an organized collection of information or data.

Nowadays there is a large stream of information, and the challenge is to store it in a way that you can easily find and use it whenever you need it. The databases can be divided into three types:

Centralized. All the data is a unified body that is stored on one computer. To get the information you have to connect to the main computer called server.

Decentralized. It means that there is no central storage. Some servers provide information to the clients. The servers are connected with each other.

Distributed. There are no data storages. All the nodes contain information. The clients are equal and have equal rights.