Expression: What is up?

[Akshara10]

thx for the explanation..u made thyem very clear...........
Can u explain the meaning of " WHAT IS UP? " and how to respond to this question......
also explain the tenses with more examples especially the difference between present perfect n simple present

[Magda21]

it means "what's going on?" in Polish language "O co chodzi?", you give this question, for example when you welcome your friend (at least I think so). You can answer it by telling what you are doing at the moment. I do hope it' a correct explanation.
What concerns the differences between present simple and present perfect, in present perfect you focus on the result of the activity, e.g.
I have broken my leg and I can't play football.
I have known her FOR 8 years.
I have lived in Italy SINCE 1995.
While in Present Simple you haven't got such attributes, instead of them there are for instance: always, once in a blue moon= very rarely, every day, generally expressions connected with regularity. Examples:
I go to the swimming pool once a week.
My friend works from 8 a.m. to 4 p.m. every day.