Pie chart displays a single percentage. I agree with Edward Tufte that pie charts are not very useful. Which would you rather see? This graphic or the number 42%?
Discrete marks a series of values . The length of the bars doesn't change.
Bar graph builds a simple bar graph . Note the bug in the last bar -- it doesn't go all the way to the origin.
Area graphs are possible too.
The smooth sparkline builds a word-sized line graph suitable for continuous data like medical records, stock charts, temperature data, etc.