We are highly susceptible to small subconscious influences on behaviour. Priming is an implicit memory effect. Stimuli in our environment - an image, sound, word, smell, taste and even physical movement for which someone has an existing strong association - may prime us and later affect our responsiveness to something, or our judgement, and even our actions and motivations.
We are unaware of being "primed", even though the influence on our behaviour can be remarkable. Priming is all around us - supermarkets use the pleasant smell of baking to tempt us to buy and we even prime ourselves - for example, through our posture, what we read or our use of language.