A brand exists in peoples' minds as a network: a unique memory structure of thoughts, feelings, experiences, images, stories, associations, colours, sounds, symbols and memories. This is built up over-time from brand and product experiences, exposure to communications, word of mouth and so…
In psychology, most simply, a bias is a tendency.
'Brand essence' is a compact summary of what a brand stands for, typically as part of a more detailed brand key (eg Aaker's 'Brand Identity Planning Model' or Ipsos' 'Brand Mandala').
Brainstorming is typically used in the first part of an ideation workshop, whereby a group of 5-10 participants create new ideas or solutions to a problem by generating a large number of ideas without subjecting them to critical evaluation.
"Big Data" is a very broad term, used often - and for a variety of different purposes.