What is a placeholder for a piece of information that can change is called?

Variable.

Explanation:

A placeholder for a piece of information that can change is called variable.

In Computer programming, a variable stores information which is passed from the location of the method call directly to the method that is called by the program.

For example, they can serve as a model for a function; when used as an input, such as for passing a value to a function and when used as an output, such as for retrieving a value from the same function.

Hence, when you create variables in a function, you can can set the values for their parameters.

For instance, to pass a class to a family of classes use the code;

\\parameter Name as Type (Keywords) = value;

\\procedure XorSwap (var a,b :integer) = "myvalue";