The small and inexpensive instrument known as the "Ten Hole", the "Diatonic", the "Major", or the "Blues" harmonica (or "harp") is the most common and easily available type of harmonica, though many other types do exist. It can be used to play almost any style of music.
This instructional package is designed primarily for use with a ten hole harmonica of the above type. Make sure that your harmonica has ten holes, and is "diatonic-tuned" or "Major-tuned".
In addition, every harmonica has a small letter from "A" to "G" stamped on it, somewhere, to indicate its "key". Make sure that yours is in the "key of C" before you purchase it.