Can someone explain what "data" "clock" and "latch" mean?

I'm working on the tutorial #5 that came with the arduino (the 8 more led's with the integrated circuit). I'm confused as to what "data" "clock" and "latch" mean in the beginning of the code when you're setting the pins. Can someone explain this to me?

They are pins on the shift register.

I could never understand what was going on with shift registers, then this simulator came along.

It's a bit clearer after playing with that for a little bit - I think the "Serial Input Toggle" would be equiv to data.

Someone with more of a clue will no doubt come along in a second to help you out!

data = "this is the value of a bit i want you to shift in" clock = "now is the time I want you to take the data and shift it in" latch = "now is the time to copy all the shifted data bits to the output register so they appear on the output pins"

The shift register has an output register (memory) so the pins don't change as you are shifting bits in. Only when you tweak the latch pin do the bits appear at the output.