Yes, it means Singles Lens Reflex: SLR. That means you have one lens on your camera. Reflex means the bending of light using a mirror: therefore, the one lens on your camera bends light up to your viewing eyepiece, and the mirror moves out of the way when you take the picutre.(posted 8267 days ago)A TLR camera means: Twin Lens Reflex camera. This kind of camera uses two lenses. A viewing lens on top (with a mirror to reflex the light to your eye) and a separate taking lens on the bottom that takes the picture as with the Rolleiflex camera line.
Other cameras, such as rangefinder and viewfinder cameras do not use "reflex" mirrors or prisms, and the lens photographs one thing, and, hopefully, the viewfinder sees the same thing. Most point and shoot cameras are of this type as are some of the very, very high grade pro cameras like the Leica M series.
Hope this helps.