What's a "queef?"

What does the term "queef" mean? What causes you to do that, and what does it mean exactly? Thanks very much!
Susie replies:

Queef is a slang term for a farting sound that comes out of the vagina. It happens when air that gets trapped up in the vagina gets squeezed out. Queefs are often associated with sex because inserting an object into the vagina canal can push air up into the vagina. Because the vagina is closed in the back, the air has to escape from where it entered.