What does excatly "halli hallo" mean and when it should be appropriate to use?
So, in GERMANY/GERMAN:

What does exactly "halli hallo" mean and when it should be appropriate to use? A work? With friends? Family?

Question

What does excatly "halli hallo" mean and when it should be appropriate to use?
So, in GERMANY/GERMAN:

What does exactly "halli hallo" mean and when it should be appropriate to use? A work? With friends? Family?

Answer

1. That is used in a more relaxed atmosphere with friends or in your job with your colleagues as a greeting.  You would not say that to your boss. It is a colloquial (umgangssprachlich) expression. 
2. It is as well used to draw attention to you in a friendly way.