Image
In advertising and marketing, everything is about improving the "image" of a product or brand or a person. The image is the idea people have about it.
Image is not the real thing. An advertisement can present you with an image of a great product, that has very little to do with how you'll really experience it, which could turn out to be disappointing. Also the image you have of a product, even if it was derived from experiences told to you by friends, is not the real thing.
Because we often cannot extensively try a product before buying it, the information about it, and thereby image, is quite important. You may try a couch in a store, but how do you know how it feels when you're tired and watching TV, sitting on it? A store may have a laptop on display, but how are you going to find out how it feels when you work for several hours on it? A mortgage may seem cheap from the ads, but will it still be when the economy goes down?
Reviews
If you are to have an image of a product or brand, it is a good idea to base that on more reliable information than what advertising provides you with. On many websites reviews about all kinds of products can be found.
Not all reviews are trustworthy, as reviewers may depend on products supplied to them by companies who do want to sell these products. If they're reviewing in too negative a way, they may not receive sample products any more. It is good to check out whether reviews mention both pros and cons.
Unfortunately, companies are known to have sought to manipulate even reviews by supposed users of products. Some have hired people to write positive reviews.