Graphs then, are visual representations of worksheet data. Graphs often makes it easier to understand the data in a worksheet because users can easily pick out patterns and trends illustrated in the graph that are otherwise difficult to see.
Different types of graphs serve different purposes.
Pie Graphs -- are used to show percentages. For example, a pie graph could be used to show what percentage of your total daily calorie intake is represented by one quadruple cheese and bacon hamburger.
Bar Graphs -- are used to show comparisons between items of data. Each column in the graph represents the value of one item of data. An example of this would be to compare the calories in a quadruple cheese and bacon hamburger with the calories in a glass of water and a bowl of beet greens.
Line Graphs -- are used to show trends over time. Each line in the graph shows the changes in the value of one item of data. For example you could show changes in the values of three different stocks over a period of months.