• One or two volume pots (potentiometers)
A single-pickup guitar will normally have one volume control. A two-pickup model might have one or two: one as a master volume, or one for each pickup. Fender Strats (and their clones) have three pickups and only one volume.

• One or two tone pots
Again, no discernible method for pickup/pots ratio. These look exactly like volume pots, but tone pots are the ones with capacitors on them. (Clue #2: if you turn one up or down while playing, the tone will change. If the volume changes, odds are it's a volume pot.)

• Pickup selector switch (or switches)
Single-pickup guitars probably won't have a switch. If there is one, it's not for switching between pickups; it's for coil tapping or phase switching.
Two-pickup guitars usually have a single switch. These switches are marvels of modern engineering - by merely flipping between three positions, you get: neck pickup only, neck & bridge, or bridge only.
Three-pickup guitars generally take one of two routes: A single three-way toggle switch (that can't possibly provide every pickup combination) or three mini-switches (one on-off for each pickup).

• An output jack (often called an 'input' jack)
Here, at last, is some uniformity. No matter how many pickups, pots or switches the guitar has, it should have only one jack (unless the guitar is wired for stereo, has a synth or piezzo pickup on it, or someone wrecked the original one, couldn't get it out, and put in a new one somewhere else).
The jack's function is to prevent the escape of electrons. Think of the control cavity as a room full of rabid dogs (electrons). The only way out is through the jack, which seals itself when not in use. When a plug is inserted, the rabid dogs (electrons) rush out, and presto! They're routed through the cord to the amplifier, where they produce "hum".

• A lot of little wires running between all the parts
Experimentation is encouraged. Fire up the soldering iron & start disconnecting things! This is the real way to learn: trial & error. Errors are crucial, or it would just be called 'trial'. If you're apprehensive, make a wiring diagram before you start (although this is considered cheating by many reputable repair guys).

Note: It's helpful if you have a goal in mind when rearranging wires. General messing around, while not forbidden, usually won't improve anything.