Below you will find a file with the concepts of descriptive statistics.
Descriptive statistics are numbers that are used to summarize and describe data. The word “data” refers to the information that has been collected from an experiment, a survey, a historical record, etc. If we are analyzing birth certificates, for example, a descriptive statistic might be the percentage of certificates issued in New York State, or the average age of the mother. Any other number we choose to compute also counts as a descriptive statistic for the data from which the statistic is computed. Several descriptive statistics are often used at one time to give a full picture of the data. Mean, median, mode, variance, and standard deviation are some examples of descriptive statistics.
A nice tutorial can be found http://onlinestatbook.com/2/introduction/descriptive.html.