It has two meanings, basically. A doctor who examines you might ask you to stick out your tongue, to look for any obvious illness, many of which show up on the tongue in some way. I don't know how it is in your society, but in western societies, sticking out your tongue is an insult, a way of saying "I don't care WHAT you think!" or "You look like a fool, now". It is used more by children.

I understood you, kevinzim:) Thanks for your answer:)

:p