Kung Fu is often thought to be a Chinese Martial art. We've all watched a Kung Fu movie in our day and the characters always have amazing martial arts skills.
However, "Kung Fu" is literally translated to "one who is skilled". This means that "Kung Fu" is not a type of martial art, but more accurately defines someone who is skilled at something. This could be anything. You could be Kung Fu at snowboarding, baseball, cooking, or even picking your nose... although we don't recommend this last one.
This term has commonly been applied to "one who is skilled at a martial art", which is why "Kung Fu" movies always involve amazingly skilled martial artists.
While Kung Fu is not "officially" recognized as a form of martial art, there are many derivitives of martial arts styles originating from China that have been named after Kung Fu. While you search for a martial arts school to practice at, keep in mind that Kung Fu isn't a traditional style of martial art and most likely signifies that the style being taught is of Chinese origin. This doesn't mean that something called Kung Fu isn't a great thing for you to learn, so keep an open mind as you should with all martial arts styles.