Big data definitions

Before digging into this world made of huge amount of data, streaming data flows and anayltic applications, let's fix some basic ideas.
Let's define the ground concepts of this world.

Big Data

Big data usually includes data sets with sizes beyond the ability of commonly used software tools to capture, curate, manage, and process data within a tolerable elapsed time. Big data "size" is a constantly moving target, as of 2012 ranging from a few dozen terabytes to many petabytes of data.