How many types of notebook cards are there???

I bought a N1 router and N1 wireless notebook card for my laptop. It doesn't fit the slot!! Are there more than one type?? I thought there were are pretty much standard. It fit my mother-in-law's slot in her laptop, she has a different dell laptop than mine. But I look in the slot and it doesn't even look the same as hers. The plastic thing that came out of the slot is got a notch in it instead of being completely straight across the bottom. If I am making no sense I am sorry, I am trying to explain the best way I know how. Anyway, the slot is the same width as the card but when I tried to put it in the slot it wouldn't go in all the way. Looked like something was blocking it, then when I looked down in the slot it looked like it had a pin board that was not near as long as hers is and a black thing next to it that was what was keeping the card from going in. Doesn't make any sense to me?? Does it make any sense to you or am I speaking another language?? Sorry if I am not too clear on the details. Just need help to find out what is the deal with it?? And how I find out what kind of slot it is and what kind of card it takes??