Big Data, as the name implies, relates to very large sets of data collected through free or commercial services on the internet.
This massive amount of data arises from sensors, posts to social networking sites, digital images, videos posted online, transaction records of online purchases, and from mobile phone GPS signals to name a few.
A couple of aspects of big data worth noting are:
it is impossible to remove/withdraw information from big data – information once added will persist indefinitely in the cloud
virtually any information that is stored electronically, including information within personal devices, offline data storage, even information thought to be deleted, has the potential to be included in big data.