Help, this thing on the front of my laptop came out?!?

It's a little part that sticks out in the front of my laptop, right where you pick the top of the laptop up to open it. It has labeling near it called SD/MMC- MS/Pro. What the hell is it? I guess my desk was pushing up on it and I tried to pull it out and it just came out, what is that piece? Did I break something? It's an all black Dell laptop, btw. INSPIRON