עלי = This word can be used in different ways:
על לא דבר = like "you are welcome" a response to "thank you"/
על מה אתה מדבר? = what are you talking about?
זה לא מקובל עלי = I don't accept it!
סמוך עלי = trust me
אל תסתכל עלי = don't watch at me
In colloquial language:
בוא ניפגש, הקפה עלי = let's meet, I pay for the coffee (a generous invitation)
לשכן שלי יש פרארי, הלוואי עלי = my neighbour has a Ferrari, I wish I had too
הוא מת עלי = he loves me very much
As you can see, to ask about על or עלי is like asking about "by" in English..