For Example: F4DZ-2B120A -- a RH brake caliper

F means 90 (E is 80's, D is 70's, C 60's, B is 50's, A is 40's)

4 is the year within the decade that the part first was installed by Ford, so an F4 part was first used on 1994 model year cars

D is the line of car :

A is full size Ford
B is Fairlane/Torino to 76, then 77-79 LTD II, then Festiva, then Aspire
C is Mercury Capri (60's - 70's), Escort
D is Maverick, Granada, Taurus, 96 and later Taurus/Sable common parts
E is Escort
F is common Tempo/Escort parts (same parts, different body panels)
G is Mercury Montego, Monarch
H is Ford heavy truck
J is marine (boat engines, stationary power plants)
K is Tracer
L is Lincoln Mark series and regular 4-door Lincoln
M is full size Mercury for unique parts (otherwise, use A)
N is Ford tractor
O is Mercury Montego, Sable, and Lincoln Continental
P is Bobcat and Pinto
R is Merkur, then Contour/Mystyque
S is T-bird
T is light truck, Bronco, Explorer
U is Econoline can
V is Lincoln Town car
W is Cougar
X is Villager
Y is Lincoln or Mercury/Lincoln non-vehicle-specific part
Z is Mustang or Ford non-vehicle-specific part
2 is Probe
3 is Tempo
4 is 96+ Sable body parts
6 is Topaz
7 is Ranger
8 is Windstar
9 is Aerostar

-2B120 is the basic part # and is the number for the caliper.  If part of a pair, then the lower number is the right hand side (i.e. 120 is right, and 121 is left).  The only exception is power window motors for only one car.  Series means the 1000, 1001, .... 1999, 1A001, to 1Z999 where every basic part number is a unique part on a car, and the same part 'name' for a
different car is differentiated by the prefix.

1000-2000 series are wheels and brakes
3000 series are front suspension and steering
4000 series are rear axle and drive axle
5000 series are frames front stabilizer and rear suspension
6000 series are engine parts
7000 series are MTX transmission and clutch, A7000 series are ATX transmission
8000 series are cooling and grille
9000 series are fuel
9500 series are carburator
10300 series and up are generator, alternator, starter, distributor
13000 series and up are lamps, wiring, and electrical except for 10300 series
16000 series and up are fenders and hood
17000 series and up are speedometer and associated parts
17500 series and up are bumpers, jack, mirrors, washer/wipers, speedo cables
18000 series and up are air conditioning, heaters and radios
00000 series are body front (door posts and ahead and floor pans) including
instrument panel and dash, but not gauges
23000 series and up are body sheet metal and exterior rubber bits
40000 series and up are back half of the car (trunk, roof racks, T-roof etc)
50000 series and up are exterior mouldings, emblems, and nameplates
60000 series and up are seats
70000 series and up are doors, windows, (not windshield), seat trim/covers
Japanese weird parts use 2-piece Mazda part numbers

Note that if your '96 car has a part number such as F4DZ-2B120A, then you know the part was first used on '94 cars, was installed on '95s and is still being used unchanged on '96s.

Part #'s are not necessarily the same as casting #'s or the numbers on the part.  Line numbers are different still.