Where does OSX put my iTunes playlists?

My new MacBook is 10.5.4, and my previous desktop 10.4.7. I have all the data from that computer available to me, and I'm building a new profile (rather than just working from an imported old one). I was able to import all my iTunes music successfully. Tell me please, where is the data containing my playlists for iTunes? So i can copy it over.

Thanks in advance for any help.

How to use your iPod to move your music to a new computer
How to back up your media in iTunes
Back up your iTunes library by copying to an external hard drive

Thanks so much Technologist. Those are great references but i can't copy via my iPod it's a shuffle, and don't really need to put my whole library on a DVD as it's all already on my HD, no problem. iTunes loaded it, i just need to know where iTunes would store my playlist info in my old profile if possible, so i can drag it to my new one. Thanks to anyone who has this information. Peace.