A googol has 100 zeroes in expanded notation, and in exponent notation, it is 10 to the power. A googol is written by writing the digit one and then putting 100 zeroes after it.
The term googol goes back to 1938 and comes from Milton Sirotta, a 9-year-old kid. Sirotta is the nephew of Edward Kasner, an American mathematician. This number first made an appearance in the book "Mathematics and the Imagination" in 1940. There are other terms to describe a googol, and these include the long-scale term ten thousand sexdecillion, the short-scale term ten duotrigintillion and the Peletier long-scale term ten sexdecilliard.