Why is there a difference between GDP and real GDP? details below?

Question

the imaginary island of Morania has a GDP of $12,000 and a real GDP of $10,000.

explain plz

Answer 1

It means that difference were because of changes in price level, or inflation was

100*(12'000-10'000)/10'000= 20% from initial base-period.

If population is 500 people then per capita real GDP is $10'000/500= $20