What is DSLR?

DSLR stands for Digital Single Lens Reflex

It is called single lens reflex because in this design light travels through a single lens, an internal mirror is used to direct the view from the photographic lens into the viewfinder. When one takes a picture this mirror flips up (cause the clicking sound) and allow the light to hit the sensor. Unlike the compact cameras one can have more prominent view through the view finder because in compact camera the viewing angle of viewfinder and that of a sensor are different which result in the different images i.e.  the image one is going to capture will be different from what we are seeing through the view finder.

Further unlike the compact/point-n-shoot digital cameras SLRs have real time optical view through which more precise and accurate operation can be performed, compact digital cameras have electronic LCD screen through which one can see the digital representation of the view.

The below picture will help you to understand the functionality difference between a compact camera and DSLR camera.