A googol is a large number defined as 10 raised to the power of 100, or 1 followed by 100 zeros. It was first introduced by mathematician Edward Kasner in the early 20th century. The term was created by Kasner's nine-year-old nephew, who suggested the name to represent this enormous quantity. To put a googol into perspective, it is much larger than the number of atoms in the observable universe, which is estimated to be around 10^80. The concept of a googol helps illustrate the difference between finite numbers and the vastness of mathematical possibilities.