What Is Big Data?
http://www-01.ibm.com/software/data/bigdata/

Every day, we create 2.5 quintillion bytes of data — so much that 90% of the data in the world today has been created in the last two years alone. This data comes from everywhere: sensors used to gather climate information, posts to social media sites, digital pictures and videos, purchase transaction records, and cell phone GPS signals to name a few. This data is big data. This will be added to Statistics and Big Data Resources Subject Tracer™.