1)            Graphs of one variable, include bar graphs and pie charts.  They show information/facts, give a description of what is.  For example, bar graphs will have a number/variables on the y axis, and several distinct components on the x axis.  The value of each component on the x axis is measured in the single variable shown on the y axis.  A pie chart has a similar approach (except the variable is always a percentage and should add to 100%).

Another example is a time series graph, where the x axis shows different periods of time, but these are