Weird symbols for key combinations on a Mac

Where am I supposed to learn the meaning of the weird key-combination symbols on a Mac?

I'm specifically talking about the hollow up arrow, the broken switch circuit symbol, the hollow up arrow with a hollow square under it, the caret, the forward arrow with a bar or pipe in front, and the circle with an arrow leading out of it. The only weird symbol I have actually drawn on my keyboard is the command symbol which is like a clover. The other symbols I mentioned respectively mean: shift, option(alt), caps lock, control (only one I got right away), tab, and escape (the most frustrating one).

Clearly these must be documented somewhere (although why they're not on the keyboard is very odd to me) but where are they discussed?

Update: I totally forgot the other, much sillier ones: strike-through caret is enter (number pad), up-left arrow is home, down-right arrow is end, and the fairly more obvious right, u-turn, left arrow is carriage return.

!

I'm missing an image for caps lock, but you see what I mean. I've seen some app short cuts as: which leaves me wondering okay, command-option, what?

Here's the images from Apple's 10.6 article which isn't nicely formatted:

Here's a chart from OS X Keyboard Shortcuts that lists all the main icons, their primary names, and alternate names/symbols:

This Apple fansite has a similar list on a page with other Mac hints.

OS X Keyboard Shortcuts also provides descriptions for the most commonly seen icons. This official Apple site is similar, but is targeted at new users making the switch from Windows.

And as a bit of historical trivia, this Folklore.org blog post explains where the Command icon came from. The original idea was to use the Apple logo, but Steve Jobs decided there were "too many Apples on the screen!" and ordered a change. The icon you call "weird" and "like a clover" actually started life as the campground symbol on Swedish road signs.

I remember seeing some of these icons drawn on the keyboards of older Apple computers; why they were discontinued, I don't know.

_{(An earlier revision of this answer contained links to Apple documentation that stopped working.)}