"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.
Planck time is the name given to the smallest known unit of time. It's a little confusing but it measures the amount of time it takes light to travel 1 Planck length (a distance so small that it can't even be measured!).