Most DSLR manufacturers offer a range of models which include at the "top end", full frame sensors and in the lower price range, cropped sensors. The full frame sensor can be equated to the size of the old 35mm negative. The surface area of the cropped sensor tends to be 1/1.5 (67%) or 1/1.6 (62.5%) of that of the full frame sensor.
So what does this mean to the photographer?
When shooting with the same lens (ie: same focal length) the full frame sensor will be exposed to a larger field of view for capture. ie: it sees a "bigger picture" The cropped sensor will actually crop the overall image. This can be seen in the reference image here in this blog.
So when peolple start talking of zoom factors with cropped sensors, the implication is that a cropped sensor will give you "more zoom" for a given lens. The truth is, the cropped sensor will crop the scene as compared to a full frame sensor, it does not actually make the image larger or magnified.
With a full frame sensor, the subject can be made to occupy more of the post production image frame by cropping and hence "discarding" other information originally captured. If you always work on a copy of your original image, then you will have the option of having the "full picture" to use at a later date.
With a cropped sensor, you will have cropped the scene during capture and not have the extra detail available to revert back to at a later date.
Remember, Crop Factor is precisely that, not Zoom Factor.