The document discusses different types of data and graphs. It defines primary and secondary data, with primary data being collected by an investigator and secondary data obtained from other sources. The document then defines different types of graphs - bar graphs, double bar graphs, and pictographs. It provides examples and definitions of each graph type, including how to read and construct them. Bar graphs show data using vertical or horizontal bars, double bar graphs show two data sets for comparison, and pictographs represent data pictorially using symbols.