Google cloud is almost same like Amazone cloud services. With both, you are buying or renting computer processing power. Lets say you want to do some data processing which requires massive server processing power but you dont hav the hard or resources to do it.
What do you do? You rent for the period you want from either google or amazon.
Google drive is mainly for personal use. Its like carrying a memory stick around in your pocket but on this its available where ever you have access to internet.