A logo is an identity. Logos and marks have been used to identity groups, landmarks or business. Custom symbols/emblems are used to identify and sometimes also describes the business or group and their activities. Today we see logos everywhere from laptops to the very cloths we wear. To find out the first use of symbols we should go to religions. In ancient religions people used symbols to identify different gods, religions, meeting places, etc.
In the competition to capture market different business houses came up their own symbols to differentiate themselves from others. Defining through symbol is the most popular way to make people recognize a single entity. A logo can be a symbol which is easily recognizable or an icon or image and even a simple typography can be used as a logo to identify a particular entity. As a new entrepreneur, you need it most, because there are already a lot of brands in the market competing with you.
Brands may contain some images, some texts or both. This is like an attachment, when a brand logo is presented, the whole product concept is presented. This is how IBM, Microsoft, Google did business. This will tell you what your company name is and how popular you are.
Modern marketing strategies are depending on identity and differentiating products. From industrial age at 1920s, people started branding formally to identify their products. What will people do if the same product is offered by two companies? Color, shape, tastes can be differentiated, but the easy way is logo branding. This is how logo suits for you.