What am I?

It is in a little black case that i use to carry it around for those special moments that just need to be remebered. You can always find me with it but sometimes it just needs to sit home and charge. When i want to do something with it I put a little card in it so it can save some things. I open it up and a very bright light sometimes flickers for about a second. Than I go back in and wait for my turn to be plugged into the computer so I can go on Facebook. What am I.