The difference between faucet sizes are as follows.
Centerset: A style of a faucet that has a combined spout and handles. Center of handles are 4" apart. Also a single handle faucet installed on 4" center-to-center faucet holes.
Minispread: A special style of a faucet having separate spout and handles, but designed small enough that it will fit 4" center-to-center faucet holes.
Widespread: A style of a faucet having separate spout and handles. Usually 8" from center to handle to handle. Some widespread faucets can be set with handles up to 12" apart.
Single Hole: A style of a faucet that needs only one hole cut out of the counter top to complete the installation. It has the handles included on the faucet itself.
Wall Mount: A style of a faucet that is connected on the wall usually used on tub that has no deck.