Why is my mom like this?

I'll explain something to her and then a few seconds later she'll ask a question about what i just explained . ughhhhh and it's so frustrating talking to her and then my response is i'll just stare at her then look away then she'll get mad at me. and say that i gave her attitude. i know that what i did was a sort of a bad reaction but why does she do this all the time constantly even to other people......... so, please just tell me why she does this all the time.