Graphs are visual representations of data that help to illustrate relationships and trends. Common types include bar graphs, which display categorical data with rectangular bars, and line graphs, which show changes over time by connecting data points with lines. Pie charts represent parts of a whole, using slices to indicate proportions. Another type is the scatter plot, which uses dots to represent values for two different variables, helping to identify correlations. Histograms are similar to bar graphs but are used for continuous data, showing frequency distributions. Each graph type serves a unique purpose in data analysis and presentation.