A brand is the representation of the product: something that identifies it in a recognizable way. This could be a name, a logo, colors, writing style, or other media forms such as sound marks.
A brand is the product’s reputation, which creates certain customer expectations about the product. In other words, once customers recognize the brand representation (definition #1), they also project specific attributes onto the product — maybe that it will be high quality, healthy, or allow them to be seen as trendy or fashionable.