In a marketing context, a brand is how people perceive your product, service or organization. It’s what people think of you. How they feel about you. And why they support you.
Vital, impactful brands are built on truth and continuity. They are what they say they are. And they are united in how they say it, so you never confuse them with competing brands. That’s why so much emphasis is put on the conformity of brand language and look, and why all brands have guidelines like this one.