10" two-way loudspeakers are pro audio loudspeakers that feature two different speaker types for producing full range sound. In this case the woofer size is how we define 10 inch, because the low frequency transducer (woofer) is ten inches around.
The high frequencies are the second device we find in a two-way speaker system. A high frequency device can be a piezo tweeter, a titanium compression driver, an aluminum compression driver, a ribbon driver, a Mylar driver or a dome tweeter as well as a few other types I have forgotten to mention. Basically, when you look at a ten inch two-way pro audio loudspeaker, you will definately see a ten inch woofer, and some sort of device for producing high frequencies mounted directly above the woofer.