Big data refers to the large volumes of data that are constantly being generated. This document discusses how big data is being generated from various sources like stock exchanges, aircraft sensors, phone calls, and online banking. It then discusses using public cloud infrastructure and services like Amazon Web Services, Microsoft Azure, and Google Cloud Platform to analyze and manage big data using tools and frameworks like Hadoop. The cloud provides scalable and cost-effective options for organizations to build big data solutions without having to make large up-front investments in hardware.