Whats this thing about slices and web pages ?

[White Light]

I know the title of this post automaticly proclaims my small understanding of PhotoShop, but I have a question and I'm sure you've got anwsers.
The issue I am facing regards the process of creating a web page in Photoshop. I've got the design all done and I've published some pages using Front Page. My question is, why are slices necessary, and how will they improve my a web page ?
Any and all info will be appreciated.
Thanks, Daniel
Priority1One.com (http://Priority1one.com)

[Chonny99]

"A slice is a rectangular area of an image that you can use to create links, rollovers, and animations in the associated web page.
Dividing an image into slices gives you better control over the function and file size of your image.
You use slices to divide a source image into functional areas. When you save both the image and an HTML file, each slice is saved as
an independent file with its own settings and color palette, and the proper links, rollover effects, and animation effects are
preserved." from the Photoshop CS2 Help center