A logo is the identity of a company; it's what people identify with. The main goal of a logo is to create an impact in one single design.
A logo is a symbol, trademark or emblem that identifies the goods and services of a business on an external product, or can be used to identify an organization.
Logos are designed to work in different color schemes and at different sizes. That's why it is so important that they can be used easily in any situation and they don't take up too much space.