"What are you doing?"
Translation:तुम क्या कर रही हो ?
Whenever raha/rahi gets involved, you can be sure of it being a continuous sentence. In other words "ing" will definitely be involved in the English counterpart of that sentence.
What do you do - Tum kya karti/karte ho.
What do you do for work - Tum kya kaam karti/karte ho.
If you are speaking about कर, कर्मा, करता - कर is the verb stem of करना. कर्म is, to put it simply (but it's much deeper), the universal law of cause and effect (everything you do has karmic consequences, good or bad, that come back to you, usually in future lifetimes). करता is the masculine singular conjugated form of करना .