Let's look at the kanji for wind, which can be read "fuu", "fu", or "kaze". The on-readings are "fuu" and "fu", and the kun-reading is "kaze". On the right you can see an example definition for this kanji. Notice that the on-readings are in capitals, and the kun-reading is in lower-case. This is a standard convention used by most kanji dictionaries, to help you distinguish between the two.

Notice that when the kanji is used as part of a compound noun (e.g. "taifuu" or "ofuro"), an on-reading ("fuu" or "fu") is normally used. If you click on any of the other kanji that combine with this one, you'll see from their definition pages that they also use on-readings when forming compounds (the "wa" in wafuu, for example).