what is hafilat card and, its functions i am new in dubai?

I am new in Dubai and someone told me about a Hafilat card. I do not even know what it is. I went to a metro station yesterday and asked for a Hafilat card. The man looked at me strangely. He said something about Abu Dhabi. I did not understand. I just stood there confused. Then I went to a bus stop and tried to tap my credit card on the reader. It did not work. People behind me got angry. Today I went to a customer service center and asked for help with my Hafilat balance. The lady sighed and explained something about Nol cards. I still do not get it. I am so confused and embarrassed. I have been carrying the wrong card for days and everyone thinks I am foolish.