What is parametrization? How many parametrization types are available with QTP?

Parametrization is a process of replacing all the constants within the test script into variables (parameters) so that we can reuse the same script with different sets of test data.

Types of Parametrization in QTP:
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1) Test/Action Parameters (Input Parameters, Output Parameters)
2) Environment variables (Built-in Variables, Internal Variables, External variables)
3) DataTable Parameters (Global Sheet Parameters, Local Sheet Parameters, Run-time table Parameters)
4) Random Number Parameters