幹嘛，繁體字 干嘛，簡體字

do you mean 乾媽?

I just want to say this is informal phrase to say 'what?' for instance, you're stopped by your friend. then you can ask:幹嘛? That would be weird if you speak to your boss this. you can use '有什麼事(情)嗎?' to boss or elder. more plite :)

both are same.

Thank you for both your answers. You made it very clear for me to understand :)