Difference between current and constant prices, and the GDP deflator

CFA Level II
#1

This is LOS 20c… but what the hell is the GDP deflator? I have checked the books but cannot find anything. Can someone shed some light?

#2

gdp deflator is the number you need to divide nomial gdp to get to gdp in real terms

#3

It’s like an inflation index except it has a different composition