Simply put its a freaking big number. In the decimal system its equal to 10^24 or
1,000,000,000,000,000,000,000,000. Thats one septillion.
In binary its equal to
Me: Hey do you know a yottabyte is equal to 1,125,899,906,842,624 gigabytes? You could also call that a petagigabyte
Dude: Your a geek.
Me: I know...