Central tendency is the idea that when using normal data, all three of the main measures (mean, mode, median) tend to be roughly the same.
Standard deviation is the measure of variation in a process. Describing variation by standard deviations lets us easily compare processes.
Dispersion is the degree of variation in the data. In other words, the extent of the spread of values from the mean.
Box plots are graphical tools that let you easily visually compare variation between the data sets evaluated.
A stem and leaf plot is a technique to categorize either continuous or discrete values. It is used to organize data as they are collected.