1. used when something interests you or causes anxiety or worry, or when drawing attention to a specific matter or issue
As an adjective, something which 'concerns you' or is ‘concerning’ describes something which causes you to worry or spend time thinking about it. You could have a ‘concerning problem’ or a ‘concerning situation’, for example. You might respond to some news or an update with ‘that is very concerning’. As a verb something upsetting or unusual might 'concern you' or worry you. You can use these words in any context, social or professional.
2. used to indicate the focus of conversation or sentence
talk to sb concerning sth
If we say something such as a letter or an email is concerning something else, it means it is about that subject. For example, a school might send a letter to parents ‘concerning’ their son or daughter, or you could attend an event ‘concerning’ the environment. If something 'concerns something else it is related to your interest or involvement in something 'as far as I'm concerned', or 'as far as that (matter) is concerned'. Someone might tell you that something 'doesn't concern you' to let you know that it is none of your business and you shouldn't interfere. You can use these words in any context, social or professional. This use as a verb is usually found in professional contexts.