Arusha savanna is the central savannah at AKL-Jambo. Jambo is where all of the normal resort rooms are located. There are 2 other savannas which also have Jambo rooms facing them - Uzima and Sunset. Arusha view costs more and seems to be popular. I personally don't think it's worth it to pay the extra for Arusha as I like the other 2 savannas and the animals on them just as much - but others prefer Arusha.
There are maps here on Dis that will give you a sense of AKL's layout.