The term 'logo' and 'brand' are terms that are interchanged so loosely. They are often mixed up!
Let's get one thing straight: Logos ≠ Brands
What is a logo?
A logo represents the brand. It's a symbol of the company, product or idea. The logo taken on its own sans the story is just a glyph.
A logo is defined by company
The measure of a good logo is readability, clarity and memorability.
A good logo can make your brand much memorable. but it can't save a bad brand. A logo is a multiplier of the brand.
The Nike swoosh is just a check mark if not for what it stands for.
The Apple mark would be mistaken for a fruit company had it not been drilled into us that they make computers.
What is a brand?
A brand is reputation. It's everything. from the typography, to the way you talk to your audience, to the colors, to the graphic, it's also the product, strategy, your culture, and after sales, it's everything.
The measure of a great brand on the otherhand, is consistency, considered and a lot of intangibles
Are you reliable? helpful? exclusive? accessible? friendly? snotty?
Think of it as a logo is a physical manifestation of the company, and the brand are the beliefs, the personality, the quirks of the company.
A good brand can succeed without a great logo but a good logo will never suceed without an excellent brand.