What is exponential growth ?

According to legend, the game of chess was invented by the Brahmin Sissa to amuse and teach his king.

Asked by the grateful monarch what he wanted in return, the wise
man requested that the king to place one grain of rice in the first square of the chessboard, two in the second, four in the third, and so on, doubling the amount of rice up to the 64th square.

The king agreed on the spot, and as a result he was the first person to learn the valuable (albeit humbling) lesson of exponential growth.

Sissa’s request amounted to 2⁶⁴ −1 = 18,446,744,073,709,551,615 grains of rice, enough rice to pave all of India several times over !