There has been much controversy surrounding the issue of subliminal messages but what are subliminal messages? There is no easy answer to this question but simply put it is a message that bypasses your conscious mind and goes strait to the subconscious mind.
So, if you made a new years resolution to loose a few extra pounds and you hear this little voice in your head saying "nooooooooooo, this will be torture, I will never be able to follow through with this," then you understand the problem with ideas going through your conscious mind. What if you could get the message "I like healthy food" into your mind without your conscious mind saying "no you don't"? Well, that is the theory behind subliminal messaging.
There are many techniques used to transmit subliminal messages. It can be embeded in audio or visual things. One method is to flash text or a picture in a video for a verry short amount of time. In fact, the time is so short that you cannot conciesly percieve what this picture is. However, your subconcious mind can. In that way an you can avoid those voices in your head telling you it is impossible!
When it comes down to it all video, all audio, and even all writing is filled with subliminal messages. Or rather semisubliminal messages. These kind of messages can be examined if someone is careful but is not always easy to examine. When a writer writes some emotional story about love and sex that book is filled with the authors views on love and sex. Those ideas will many times be transmitted directly to your subconsious mind without ever being filter by ones concious mind. The majority of the US simply follows the media and the ideology of tv. This is in fact the result of semisubliminal messages.