To hear about

i. (To hear, find out what has happened to someone)
A: Have you heard about John?
B: No, tell me.
A: Unfortunately he has lost his job.

ii. (To find out about something)

– found this school in the Yellow Pages. How did you hear about/of* it?
– I was very happy to hear about/of* the recent addition to your family.

*Note that To hear of can be used in the same way
as To hear about for this meaning only.

(To receive information about someone/something from somebody
else – e.g. reputation, character etc.)

At long last we have met; I’ve heard quite a bit about you.

I’m surprised you haven’t heard more about our company;

we’ve got quite a reputation.*

*There is a slight difference between the above sentence and “I’m surprised you haven’t heard of that company…..
which means that the person being spoken to does not know that the company exists.
The sentence above (about), on the other hand, suggests that the person is aware of the company’s existence but knows nothing more about it.