Crop factor provides a difference in the focal length of the lens which usually occurs on APSC cameras. For example, if you have an 18-55mm lens, on an APSC camera the actual focal length is 27-82.5mm. In contrast to full frame cameras, the focal length remains the same, 18-55mm.
The size of this crop factor varies for each type of camera, depending on the size of the camera sensor. For full frame cameras the crop factor is 1. On APSC Nikon cameras the crop factor is 1.5 while APSC Canon is 1.6. The smaller the sensor used, the larger the crop factor number will be, for example on MFT (micro four thirds) cameras the crop factor number reaches 2. Likewise with Olympus and Panasonic cameras, the crop factor is 2.
Source: http://www.infofotografi.com
So, if you want to get a focal length equivalent to an 18mm lens on a full frame camera, then you can use a 12mm lens on an APSC camera.
But the advantage of an APSC camera is that if you want to shoot long distances, it will be easier to use this camera.