In short, big data is large sets of unstructured data. Traditionally, the data that we analyze has already been formatted into nice rows and columns. Think of a spreadsheet with a list of customer names and email addresses. The reason why big data is hard to analyze is that the data sets are massive and complex. They might contain the messy natural language we find in Tweets and Facebook updates, so the challenge involves sorting, analyzing, and processing. But as the data sets are so large and layered with information, good analysis can reveal surprising insights.