I guess in means being skeptical. You don’t accept what someone says as truth without verification.
I suspect most people do it naturally, but I suppose there are credulous people who take things that someone says as gospel without any other verification. I don’t know.
Frankly it sounds like a mysterious name for something that seems pretty ordinary to me. Academics like to do that, I’ve found. They have about ten different names that essentially mean the same thing as reading. “Content analysis.” “Qualitative data analysis.” “Narrative analysis.” Hermeneutic analysis.” Etc. All the same thing, and probably all the same a critical thinking.
Life is a puzzle. Figure it out. What does it mean? That’s what we all do all the time. But academics (and I work for them) love to take something simple and give it a fancy new name so they can write about it and pretend they invented it. Then all the credulous little grad students read about the theory and think it is sexy as hell and they run around thinking how smart they are. But it’s all just thinking. Like most people do every day.