That's any computer, not just Macs.  It's very good info though for people that don't know.

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From: SciArt-L Discussion List-for Natural Science Illustration- [[log in to unmask]] On Behalf Of Kalliopi Monoyios [[log in to unmask]]
Sent: Friday, August 08, 2008 4:08 PM
To: [log in to unmask]
Subject: [SCIART] mac's big bad secret?

Hi all, forgive me if you know this already but I just learned a
priceless Mac tip from our Computer Dude. Apparently anything and
everything that is on your desktop is stored in RAM (Macs only, I
think). Therefore, if you're like me and have a folder with seven years
of work sitting on your desktop for easy access, you're inadvertently
tying up all of your computer's RAM & slowing everything down. I
discovered this b/c I was asking him about defragging since it has come
up as a thread recently on this list. His suggestion to try clearing the
desktop first.

Computer Dude suggests keeping all of the files you create in your
"Documents" folder and then creating aliases to put on your desktop. He
says to keep the files on your desktop under 500KB and your computer
will run like the day it was born. I ran home and tried it on my ancient
laptop and sure enough, programs that were painfully slow before are
opening with lightning speed and zipping along happily. What a tip!

Hope that's enlightening to some of you. I feel like I just made a
million bucks! (time is money, right?)
Kapi