Priming is the pre-activation of a mental representation for the purpose of affecting behavior in the near future.
There are many examples in our daily lives where we are subjects of priming. Even if we are aware and resistant to it, we are primed subconsciously. An example of priming is presenting positive images in an ad for a product. The next time the viewer sees the product in a store their memories of the positive images they saw in the ad will be triggered which will create positive feelings towards the product.
It is important to keep in mind that as soon as your visitor arrives at your site you have the opportunity to prime them by using color, text, metaphors, images, videos and audio.
Priming is another tool in a UX designer’s tool belt to improve the perception of your product.
P.S. Just make sure you are ethical about it.