What's a brand identity?
First we must understand what a brand is; a "brand is the sum total of how someone perceives a particular organization. Branding is about shaping that perception." (Ashley Friedlein) This feeling can be shaped by the way your brand looks, feels, thinks, speaks, sounds, tastes, and smells.
Now, a brand identity is everything that can influence someone to have an opinion about your brand: a name, logo, color palette, graphic elements, print, tone-of-voice, messaging, photography and video, packaging, sound/jingle, website, etc.. Basically, a brand identity is the foundation of everything you do and who you are.
This is not to be confused with marketing, as marketing could not exist without a brand identity. If you market something without a brand identity, how will your consumer know what you're marketing? Yes, they might know you are marketing a car, but what car exactly?