A good way to start thinking about the complexities of big data is called the four dimensions, or Four V's of big data. This model was first introduced as the three V's by Gartner analyst Doug Laney in 2001. The three V's stood for Volume, Velocity, and Variety, and the fourth V, Veracity, was added later by IBM. Gartner's official definition states the following:
"Big data is high volume, high velocity, and/or high variety information assets that require new forms of processing to enable enhanced decision making, insight discovery and process optimization."
Laney, Douglas. "The Importance of 'Big Data': A Definition", Gartner
Laney, Douglas. "The Importance of 'Big Data': A Definition", Gartner