I am working from memory...but I think I understand at least two things...
1. Folders - these are folders exactly as you have on your computer. I typically import an entire folder of pictures in. The main issue is that if you don't import the "top folder", the "sub-folder" will be listed as whatever name you give it. For example, with my personal pictures, I have a folder called March which is contained in my 2007 folder. If I only bring in March, that is how it will be listed. However, if I bring in 2007, the "tree" is shown just like in windows explorer. It isn't as big of an issue if you name your wedding "Sam-Terri-6.28.06".
2. Collections - this is a really cool feature I think. You can create various collections and put whichever pictures you desire in the collection. They do not move from the original directory, but if you click on a collection, all of your pictures (as long as they are still in LR) will show up. Think of it like keywords. For example, I have a collection of pictures I use in my opening slideshow on my site called "Home Page Show". I change the collection contents without having to resave and mess around a lot...then export the pictures out, and upload the files.
I am not sure about Catalogs...can't remember that one.
I probably did a bad job explaining it...sorry if I create any confusion.
QUOTE(Chris Humphreys @ June 27 2007, 11:57 PM)

I just started Lightroom 'bout a week ago and I LOVE it. It's sweet, but I'm still trying to figure out the way the Library works.
Maybe someone can explain it to me...
What's the difference between folders, catalogs, and collections? I'm so used to organizing he structure of how I save files on my computer through the Finder and then just accessing those structures through Bridge, and Lightroom seems to be forcing me to adapt to the Library, but I'm not really quite sure how it works and how it's set up.
It's a REALLY REALLY cool program though. I love it.