Aka mirrorless camera mirrorless cameras, is the term given to the type of digital camera technology that takes a middle position between compact cameras (compact cameras) with a DSLR camera: it has a replaceable lenses like a DSLR camera, but is not equipped with an optical viewfinder mirror.
As is known, the structure of the system optical viewfinder on a DSLR camera is quite bulky in the camera body, so that on average a large DSLR camera.
The mirrorless camera manufacturers produce cameras with the aim to provide a camera system that is capable of producing image quality that is equivalent to DSLR cameras and has a lens system (lens mount) that can be changed / replaced, but with a smaller body size than DSLR cameras. For that purpose they replace TTL / optical viewfinder with an electronic viewfinder which is more compact in size. While the size of the image sensor is held varies, the size of the image sensor to the compact camera has a sensor size equivalent to a DSLR camera (of course at a price which is more expensive).
The technical term is a mirrorless camera mirrorless interchangeable-lens camera (MILC). There was also a call to Mirrorless System Camera (MSC), Compact System Camera (CSC), Digital Single Lens Mirrorless (DSLM), and Digital Interchangeable-Lens System camera.
Pioneer mirrorless camera is Epson R-D1 (launched in 2004) who use Leica M mount. Major camera manufacturers then gradually enter the mirrorless camera market is quite popular: Sony with the Sony NEX series, the Panasonic Lumix DMC-G2 (Micro Four Thirds), with a Canon Canon EOS M that use APS-C sensor like a DSLR camera for beginners, and the Samsung NX10 (APS-C).