The var_history is used to store variables for the future.
When to use (example): You have a variable named a. You want the value in "a" for the future but you have to change a's value.
The var_history has three functions.
Using the function:
Parameters: 1. value = the value or variable's value to save to the var_history.
Using the function:
Parameters: 1. place = the number of the attempt you save your value to the var_history.
Using the function: