The document discusses big data, including the different units used to measure data size like bytes, kilobytes, megabytes, etc. It notes that big data is difficult to store and process using traditional tools due to its large size and complexity. Big data is growing rapidly in volume, velocity and variety. Some challenges in analyzing big data include its unstructured nature, size that exceeds capabilities of conventional tools, and need for real-time insights. Security, access control, data classification and performance impacts must be considered when protecting big data.