The Wikipedia article on EV is pretty good, particularly because it includes a table with the EV of common subjects:

Exposure value - Wikipedia, the free encyclopedia
The way I prefer to think of EV is as the convergence of shutter speed, aperture and ISO. EV is most appropriately expressed as n(ISO) where n is an integer and ISO is, well, the ISO number. At its basis, EV is a unit-less numeric representation of subject luminance. Here are the bullet points:

- Each number on the EV scale represents twice as much luminance as the number directly below it
- 0 (zero) is always 1 second at f/1.0 regardless of ISO
- If the ISO qualifier is missing, ISO 100 is assumed
**A difference of 1 EV luminance corresponds to a 1 stop difference in exposure**

Now for a real world example. The exposure meter on the K-50 has a listed sensitivity range of EV 0-22. Since the ISO is not explicitly stated it is assumed to be ISO 100 yielding EV(100) 0-22. To put the sensitivity in terms of exposure settings, the meter is linear and will give valid results from this minimum:

EV(100) 0 ==> the amount of light where an exposure of 1s @ f/1.0 @ ISO 100 is appropriate

Note that this is VERY dim. Below this amount of light the meter readout will blink. On the high end the meter is linear and will give valid results up to:

EV(100) 22 ==> the amount of light where an exposure of 1/4000s @ f/32 @ ISO 100 is appropriate

Note that this is VERY bright. Above this point the meter readout will blink.

Are we confused yet? If so, there is no reason for concern since it is unlikely that you will ever need to be concerned about any of the above in normal shooting, particularly if you use auto-ISO. The time it is used is when you are attempting precise determination of exposure for particular parts of the scene.*

Summary:

**You can express subject luminance in terms of a single EV number which may correspond to any of an infinite combination of exposure settings. That EV number represents twice as much light as the preceding step and half as much light as the next step in the integer series of EV values.**
Steve

* A common situation for difficult lighting conditions where you might use a hand-held meter and intend to "place" exposure on a specific part of the subject. Both of my hand-held meters provide output as EV as an option.