What is data verification and why is it necessary?

"I always validate my data because I know that imperfect, unvalidated data will likely lead to flawed business decisions down the line. And not only do I make sure to verify the data inputs and values themselves, but I also validate the data model so I don't run into issues later on using my data files in various applications and programs. I typically use validation rules that check for consistency around data type, range, uniqueness, consistent expressions, and null values, in addition to formatting rules that validate the structure of my data. "