The document discusses data visualization and pixel-oriented visualization techniques. It defines data visualization as using visual elements like charts and graphs to communicate data clearly. Pixel-oriented techniques represent each data point as a pixel, allowing large amounts of data to be visualized on a screen using color-coded pixels. The document provides examples of how pixel-oriented visualization can be used to visualize population data of countries and customer income data. It also discusses how heat maps, a type of pixel visualization, are commonly used in data mining to visualize correlation matrices and gene expression data.