A googolplex is a large number defined as 10 raised to the power of a googol, which itself is 10 raised to the power of 100. This means a googolplex is written as 10^(10^100). It is an unimaginably vast number, far exceeding the total number of atoms in the observable universe. Due to its size, a googolplex cannot be physically written out in decimal form, as it would require more space than is available in the universe. Instead, it is primarily used in mathematics and theoretical discussions to illustrate concepts of infinity and large quantities.