(plain copy/paste from http://www.phrases.org.uk/meanings/what-you-see-is-what-you-get.html) From the time that this phrase was coined in relation to computer interfaces it was also given as what has become one of the best-known of all acronyms - wysiwyg (pronounced 'whizzywig'). That time was April 1982, when the phrase, acronym and definition were printed in Byte magazine: 'What you see is what you get' (or WYSIWYG) refers to the situation in which the display screen portrays an accurate rendition of the printed page. The phrase had a life before computers. It had been used by advertisers in the USA since at least the 1940s to indicate a straightforward, no-fuss form of trading. An advert for a furniture sale in The Galveston Daily News in May 1949 comes close: Rules of This Sale No Refunds ... No Exchanges ... No Tradeins or Approvals. What You See Is What You Buy What You Get! The precise phrase comes a few years later. For instance, this text from an advert for a house sale, in The Oakland Tribune, May 1966: "So with the exception of landscaping end decorator furnishings, what you see is what you get." The phrase is also used in a general context, often by individuals to describe themselves. It is shorthand for 'I may not be perfect, but I'll be making no efforts to improve, so be warned', in the same way that people used to say 'take me as you find me'.

It means that there is nothing hidden, nothing extra unseen, good or bad. People say it when someone asks them for something more, either when they are buying something or entering into a relationship. If we are selling something, we might say "as is", meaning "you buy it as it is now, the way it is now, how you see it." So, what you see is what you get. That is, if you know what you are looking at or looking for. "What you see is what you get" doesn't help much if you are blind.