Box Plot

Also known as boxplots or box-whisker diagrams
A box plot is a way of showing a range that has been divided into quartiles.
The top of the box is always the first quartile
The bottom of the box is always the third quartile.
The band inside the box is always the second quartile.

Box Plot with Whiskers

A box plot can have lines extending vertically from the boxes (these are called whiskers) and they usually indicate the upper and lower quartiles.
The whiskers could however be used to represent other things:
1) The minimum and maximum of all the data
2) One standard deviation above or below the arithmetic mean
Any data not included between the whiskers should be plotted as an outlier with a dot.