On my camera, there is an option for Aspect Ratios. What are these. Which is the best one?

What is best depends on what you want to do with the pictures. Aspect ratio defines the ratio of the width to the height. For example, televisions either have an aspect ratio of 4:3 (standard tv) or 16:9 (widescreen). Here are some pages that might explain it for you:

http://home.comcast.net/~igpl/Aspect.html
http://www.hypermaths.org/quadibloc/other/aspint.htm

Oh, Ok thanks. Its that, I also want too make big photos, like 8x10's or something. Do I need too use a different ratio. Iam currently using 4:3. I also have 3:2 and 16:9

3:4 should be sufficient. in terms of printing, you want to increase the resolution of hte photos higher. i take photos at about 1000x1000 on my digicam and they print beautifully on 4x5 photo paper.

As a note, if you end up resizing any photos on the computer, make sure that when you deacrease the size in inches, make sure hte number of pixels in the iamge doesnt go down as well.

I would recommend the aspect ratio that uses the maximum available pixels of your digital camera. Selecting 16:9, for example, may simply black out top/bottom blocks of pixels, reducing the pixel-count of your photo. On the other hand, an advantage to setting the aspect ratio on the camera is that you can frame your subject to fit the final print.

Any digital photo can be "cropped" on your PC to any desired aspect ratio/size, such as 5X7 or 8X10. Personally, I want to capture as many pixels as I can and then crop and size after I upload the photo to my PC.