What does formatting a micro sd card do?

Essentially, formatting a memory card will erase the images and make sure that the card will work correctly with the camera.

"Formatting a card basically insures that it is going to work right with your camera.

Just like computers, memory cards have files systems, folders, etc. When you use your camera to format a card, it sets the card up the way the camera needs it to be in order to function properly."

More information at this website: http://www.worldstart.com/tips/tips.php/958

Hope this helps!