[sameerrao]

5X, 7X zoom is a relative term. So 5x of one lense is not strictly comparable to another unless both lenses have the same focal lens range.

E.g. my 12-24mm wide angle lens has a 2X zoom (max focal length/min focal length) and my 70-200mm has a 2.9X zoom.

The 5X vs 4X terminology are more significant when talking about P&S cameras which sort of have similar focal length ranges to begin with.

With SLRs, we talk about the focal length range like 12-24mm, 70-200mm, etc.

The way I see it:
10-24mm constitutes wide angles suitable for landscape photography and interesting close-up with distortion
24-100mm constitutes wide-angle to normal zoom range - this is typically the range that most P&S work at. Good for your car photoshoots for instance.
100-250mm represent middle level zoom - good for race tracks and say jet skis out in the ocean
250-600mm represents high end zoom which gives extreme maginfication and is used by wildlife photogs as well as for racetrack photography.

To get a handle of these numbers why dont you pull up the manual of your current camera and see the focal range that comes standard. This will give you a good reference to compare other lenses with.