Answer:
Brand personality is a set of traits that characterize a brand name with human qualities. For example, Apple is seen as hip and young, and Dove is seen as feminist and honest. It includes things like age, gender, class, religion, etc.
A brand personality defines how a brand is perceived by consumers, and therefore is extremely valuable to marketers and brand strategists, as it defines/differentiates the brand from all the others.
A brand personality is created from all the different attributes of the brand. This can range from the very nature of the product - for example, athletic clothing is outdoorsy, young, and adventurous, while insurance is down to earth, upper class, older; a high-priced item might be seen as snobby or rich - to the way it is advertised. The brand personality can take on the same personality as the trademark characters/celebrities who advertise/endorse the product. Even its symbol, such as the Nike "swoosh" or Apple's apple, can be strongly associated with the product and therefore contribute to its personality.