Mapping parameters and Mapping variables

What are the Mapping parameters and Mapping variables?

Mapping parameter represents a constant value that you can define before running a session. A mapping parameter retains the same value throughout the entire session. when u use the mapping parameter, U declare and use the parameter in a mapping or Mapplet. Then define the value of parameter in a parameter file for the session.

Unlike  a mapping parameter,a mapping variable represents a value that can change throughout the session.The informatica server saves the value of mapping variable to the repository at the end of session run and uses that value  next time you run the session.