If you aren't familiar with the googleplex, its a very very hugenormus number.
Million, billion, trillion.. something.. something..... something.. Uh... After a long time, a very very long time of doing this if you know your numbers, you will reach a GOOGOL.
A googol is 1, followed by a hundred zeros.
It would literally look like this:
10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
That my friends, is a Googol. This, is a HUGE number. Imagine that many tacos. That's more tacos, then there are hydrogen molecules in the known universe. That's intense.
And that's just a googol!
A Googleplex, is 1, followed by a GOOGOL zeros. Not a hundred zeros, A GOOGOL ZEROS.
Imagine every taco, turns into a zero and lines up. That's a lot of zeros.
It is physically impossible for you to write this out. If you where writing it on a piece of paper, you would need more space, then there is in the known universe.
Then why the heck would you make a number that big? Your probably asking yourself.
In the words of some guy on Yahoo answers:
it enables us to do math with very large NON_INFINITE numbers.
Which makes sense.
WHO invented it is an interesting story.
In 1938, Edward Kasner's nine-year-old nephew, Milton Sirotta, coined the term googol, then proposed the further term googolplex to be "one, followed by writing zeroes until you get tired". Kasner decided to adopt a more formal definition "because different people get tired at different times and it would never do to have Carnera be a better mathematician than Dr. Einstein, simply because he had more endurance and could write for longer". It thus became standardized to 
.
.
