Transform and Lighting, it is one of the many things for 3D acceleration. If you do a search you can find info on this.
What it does is take some of the load of the CPU and put it on the graphics card, so that the CPU can do other things that need to be done in the game you are running. I think that sums it up pretty well. If you have 136 $ to spend on a video card, then get the GeForce 4 ti4200
http://avlogic.com/product.cgi?code=11028833. It should be able to run those games a lot faster than the Kyro. If you do not have that much cash you could get an ATI 8500 or if you really do not have a lot get a GeForce 4 MX440. Check
PriceWatch for prices on these cards. Hope this is some help to you.
The card I recommend you get is the GeForce Ti4400. It has more memory than the 4200 for those games you want to play, and you can always overclock the memory and clock speeds to past the 4600 speeds. The 4200 does have 128, but it comes a lot closer to the price range of the 4400, so that's why I suggest just getting a 4400 and overclocking it.