What is a teleconverter lens?
It is a lens that fits between your lens and the camera to give the lens added length. They come in 1.4x, 1.7x and 2.0x. All of them "eat" light so while a 400mm f/2.8 becomes a 800mm when using a 2x converter lens, the amount of light reaching the film (or sensor) is equivalent to f/5.6a small lens that attaches to the back of a SLR lens which increases the focal length of the lens.
for example:
A standard 50mm lens will become 100mm when using a 2x teleconverterOr...
"Teleconverter lens" is also used to describe an accessory lens that you screw onto the front of a fixed-mount lens to give it more magnification. This would be used on a typical point and shoot camera and a "teleconverter" as described by the others above me would be used on an SLR.
