Whew! You don't ask small questions, do you?
I'll take a shot at some of these, if I leave something out or don't get something just right, other folks will chime in, until you share (roughly, anyway) the same confused understanding as the rest of us!
Whistles are tuneable or non-tuneable. A tuneable whistle has some mechanism for shortening or lengthening the whistle to change its pitch to match that of other instruments. A non-tunable whistle lacks this ability, although some inexpensive whistles with plastic fipples can be made tuneable by a simple tweak that makes the fipple moveable on the tube.
Tube -- the longest part of the whistle, which includes the holes your fingers cover. Usually made of metal, such as brass, aluminum, nickel, or tin.
Fipple -- the part of the whistle that goes between your lips and either includes the entire windway, or makes one surface of a windway with the other surface being made by the block. Fipples are often plastic, particularly a tough acetal resin called delrin is often used on high-end whistles. Fipples can also be wood or metal. Sometimes they are separate from the tube, and sometimes part of it.
Block -- a piece of wood, plastic, or metal which fits inside the fipple to form the inner surface of the windway.
Blade (or labia) -- the sharpened (or shaped) surface which breaks the airstream you blow into the whistle. The air breaking over the blade produces a stream of oscillating turbulence (via the Bournelli effect) which causes the air inside the whistle to vibrate and produces the sound.
Chamfers -- small slanted cuts on the blade side of the windway which help direct the air against the blade.
Tone holes -- the "finger holes" of the whistle.
Timbre -- the characteristic of sound that makes an organ sound different from a trumpet, and both different from a flute or an oboe.
Pure -- the tone of a whistle is "pure" if it contains no extra air and has a "hollow" sound more like ringing crystal than like an oboe; there are almost no non-musical components of the sound. Opposite of "pure" is often considered to be "traditional."
Traditional -- the tone of a whistle is traditional if it contains some nonmusical elements in addition to the tone itself, such as many overtones, extra air, little popping sounds at the beginnings of notes, rasps, squeaks, etc.
Chiff -- little popping sounds in between and at the beginnings of notes.
Backpressure -- the amount of air you have to use to make the whistle sound. Whistles with high backpressure use little air and must be blown harder than whistles with low backpressure, which use much more air. A related term is "resistance," which is how hard you have to blow.
This is just a bare beginning, hopefully others will add to and/or amend this list.
--James
Is there a list and definition of terms associated with the tin whistle? 
