It is due to the size difference between the compact camera and a frame of 35mm film. Because the imaging area is a different size, the effective aperture and focal lengths are different. To get them to a common number for comparison, you convert the smaller frame's values up to the 35mm equivalent using the "crop factor". The same goes for DSLRs, although the conversion ratio is quite a bit closer. Cropped DSLR sensors have a slightly greater DoF than full frame 35mm film/sensors. Most users can't tell the difference though in the DoF.
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