10x40.

10 = the power of the optics. The object will be magnified 10 times.
40 = the size of the objective lens. This has an effect on how much light is transmitted.

When looking at optics, you need not only look at the numbers, although there are some general guidelines. Like scopes, binoculars come cheap or good, but not both at the same time. High power does not necessarily mean good (I prefer to hunt with 8x42 binoculars myself, as the picture wobbles less when viewing than 10x, and I don't need 10x at the distances I hunt in MN) and the size of the objective only tells you how much light is let in, it doesn't tell you how good of quality the glass is.

You will have a better viewing experience with a pair of good quality binos, regardless of the power or lens size, mainly because viewing for any length of time with cheapie binos will give you one serious headache.

I would check out the buying guide here if I were you:

www.eagleoptics.com