This is a bar graph displaying reasons of why people visited the emergency room in 2003. From the graph, each bar represents a category of reason why people visited the emergency room and the height represents the number of people visited the emergency room in 2003. It is a good way to compare the categorical variable with its height.
Above is an example of a pie chart. It provides information by having the percentages of whether students are in-state, out-of-state, or international, but doesn't provide info. regarding which student is under which category. However, the pie chart is a great way to visualize and represent data with only a few categorical variables.
This is a histogram representing a graph of a frequency distribution and shows quantitative variables. It provides data regarding the percentage of students that took the SAT in 2010 in the 50 states. For the x-axis, it shows the percent range and the y-axis shows the number of states and frequency within that range. However, it doesn't specify which state is under which percent range.
Above is another example of histogram. It's a data of points scored by winner in the Super Bowl. It shows the points range for the x-axis and number of winner scored within that certain range for the y-axis. Unfortunately, it doesn't specify which winner scored under which points range.