“Introduction to the GOF Strategy Pattern in C#”:

http://www.c-sharpcorner.com/UploadFile/
    rmcochran/strategyPattern08072006095804AM/
        strategyPattern.aspx

There are three main parts to any strategy:

1. Strategy: the interface that defines how the algorithm will be called.
2. Concrete Strategy: the implementation of the strategy.
3. Context: the object holding the Concrete Strategy.

This strategy formally defines the use of the Interface.