Very simple list of terms and examples...should be very easy to understand:
Type - major design element changes:
Liberty nickel,
Buffalo nickel,
Jefferson nickel,
Seated Liberty half dollar, Capped Bust Dime,
Washington quarter.
Sub-Type - minor design element changes: With arrows, without arrows, with stars, without stars, mound reverse, plains reverse, wheat reverse, memorial reverse. (metal changes also fit into this category, i.e. - silver vs. clad)
Variety - minor changes in design not generally intended to be noticed: large date, small date, large mintmark, small mintmark, large letters, small letters, large stars, small stars,
Wide AM,
Close AM. Varieties do NOT change the sub-type.
Die Variety - flaws in die manufacture (usually involve doubling): repunched mintmark, over mintmark, inverted mintmark, doubled die, overdate, repunched date.
Die Error - problems that occur to dies while they are minting coins: overpolishing, clash,
Cud, broken die, etc.
Planchet Error - problems with how the planchets were made: Broken planchet, clipped planchet, sintered planchet, wrong planchet, wrong stock, split planchet, unplated planchet, tapered planchet.
Striking Error - problems with the presses while coins are being made: Broadstrike, off-center strike, partial collar strike, brockage, indent, struck-through, etc.
Basically any error that cannot be directly attributed to problems with the die or to manufacture of the planchet is a striking error.