What is AGP Aperture size anyway

[ITPaladin]

I have a KT7A board. In the BIOS the aperture is set to 64 MB.
Does this have anything to do with the video card memory size?
What, if anything, should I change this to in order to optimize my system?

 

[Lonyo]

This is the amount of system RAM that is accesible to the graphics card should it need more memory space to store things (such as textures). 64MB or so should be fine, but different sizes can alter performance, Search google for it, you might find a few sites that have gone in depth about it and looked at how changing it affects performance, but 64MB should be fine.