Have you watched the iPhoto tutorial?
http://www.apple.com/ilife/tutorials/iphoto/
First, you should always manipulate your iPhoto files through the application, and not via Finder. This is because any changes you make to the files and folders in the iPhoto library folder in Finder can damage your iPhoto database. To select photos for email or uploading, you can do a File > Export > File Export to a folder on your desktop, then attach or upload from that folder. This also allows you to resize the pictures to better fit an email or website. When you're done, that desktop folder can be trashed.
You can also copy a photo by dragging its thumbnail to your desktop. You can locate it by right-clicking and selecting "Show File" from the menu. A Finder window will open with that photo selected.
Now, the structure question. iPhoto stores your photos in its folder structure (which you should really not mess around in). If those folders are numbers that reflect the photo date, you have iPhoto 5. If they match your Film Rolls then you have iPhoto 6. (You've posted in the v5 forum. The structural difference is significant, so it helps to know which one you have.) With v6 you can change those roll-based folders by organizing the Film Rolls in iPhoto. With v5 they are based on the date of the photo, and only change if you change the photo's date. If you have v6 and would like more suggestions regarding organizing your rolls, let me know and I'll be happy to help you further.
Albums are virtual arrangements an do not contain actual files. They are a set of instructions that tell iPhoto which photos to display together. You won't see them represented in the Finder at all. This allows a photo to be in 50 albums with no duplication of the file on your hard drive. (That photo of you, your kids, the dog, at Christmas, can be in the album for you, your kids, etc.)
Since Albums can overlap or miss photos, I use Film Roll view to keep my library organized. This shows me my entire iPhoto inventory, that is each photo displayed once and only once. I keep my rolls closed until I need to use them, and write comments for each roll to give me a description of its contents (so I know which rolls to open). [Keeping rolls closed is a great way to optimize the loading speed of iPhoto upon launch.] I only use Albums for specific purposes, like slideshows. I recently applied keywords to every photo in my library, so with the click of a keyword I can find photos of my kids, Christmas, vacation, and any combination or exclusion of these.
Whether you prefer to use Albums/Folders or Film Rolls as your primary method of organization is a matter of personal choice. After you use iPhoto for a while you'll find the method that suits you.
P.S. Sorry to duplicate some of Lori's response. As I was writing, she posted her reply. I'm too lazy to go back and edit mine. 🙂 Kudos, Lori.
