Digital cameras are those one which take video or still photographs, or both, digitally by recording images through an electronic image sensor. It is the main device used in the field of digital photography and in this 21st century most of the cameras are digital as Digital cameras can do the things which film cameras cannot such as displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory card, and deleting images to free storage space. Most of the Digital cameras now a days can record moving video with sound as well as still photographs and even can crop and stitch pictures and perform other elementary image editing. Some of them have a GPS receiver in them and can produce Geotagged photographs too.
The optical system works just like in film cameras and use lens with a variable diaphragm to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film but in digital cameras the image pickup device is not chemical but electronic. Apart from camera phones and a few specialized types, most of the digital cameras, have a standard tripod screw.
Digital cameras are now using in many devices such as from PDAs and mobile phones which are called camera phones to vehicles. Even space telescope like The Hubble and other astronomical devices are essentially specialized digital cameras. But is there only one type of digital cameras? Certainly not my friend, a various kind of digitals cameras are there like Compact digital cameras which are designed to be tiny and portable and suitable for casual uses. Bridge cameras are higher end digital cameras that physically match DSLRs and but share with compacts the use of a fixed lens and a small sensor. Third type is Mirror less interchangeable-lens simpler and more compact than DSLRs and typically emulates the handling and ergonomics of either DSLRs or compacts. Fourth its Digital single lens reflex cameras (DSLRs) which are based on film single-lens reflex cameras (SLRs) and Waterproof digital cameras are used in underwater photography.