Recently one of my friends told me that there is distinct difference between 'know of something' and 'know about something' expressions. 'know of' is used when you have personal experience with wha... "Know about" vs.

Understanding the Context

"know of" - English Language & Usage Stack Exchange Possible duplicate of "Know about" vs. "know of". Also What are the differences between “know”, “know about”, and “know of”? on English Language Learners, which is probably a better site for questions like this.

Key Insights

to know vs to know about - English Language & Usage Stack Exchange Why do you think that He doesn't know him from his schooldays means that he does know him? It would only have that sense if you added something like In fact, he first met him at university. What is the correct usage of phrase "you don't know what you don't know"? Can it be used in formal conversation/writing? Should I use "did you know" or "do you know" to introduce a fact?

Final Thoughts

I've only seen "did you know" in action. My logical deduction is that before the "question" (which is not much of a question because you're not asking for an answer), you wouldn't have been sure whether the listener'd known about what you're about to say or not. Should I use "did you know" or "do you know" to introduce a fact?