[sdiy] Power Supply questionsss

[Chromatest Pantsmaker]

since everybody else is asking questions about power supplies, I just
recently came across something new to me.
"current limited/regulated PSU"

I understand voltage regulated, but I thought that circuits would only
draw the amount of current they needed.  THe only thing that I can
think of is that the circuit must be greedy and use as much current as
it can get, and therefor, the only way to regulate it is at the PSU.

And then....  What is a Current limited psu?  How does a person add
current limiting circuitry to an existing psu? any tips along these
lines?
thanks to all great mighty PSU gurus!
-ben (in amsterdam)  (Amsterdam, NY that is)