What do I have?

I bought a reflector telescope off of ebay.The focuser if it is a focuser moves on a slide not up and down but horizontal.The secondary mirror moves with it.Is this a focuser or is this just changing the focal length?And if is not can a focuser be mounted on top of the slide?I don't have any eye pieces for it so I can't drop one in to see if it will focus...any help will be great....thanks