What is a logo?
A logo is a symbol, a name, or trademark that represents a company and it is a simple representation and hopefully the most memorable aspect of a company. A logo is a great way to trigger memories of a particular brand. A logo is very important it is not the whole brand but at the end of the day people may forget the exact details of your website design. But a logo should be well exhibited to the viewer to be able to remember the logo of your company or logo of your website. If you think of logos like Nike and Apple these companies have such well made logos. For instance if somebody ask you to draw the Apple or the Nike tick logo you are able to do it straight from your memory and that is a part of good branding.
There is an example that explains more the logo