iPad 2 mail changes

My Inbox symbol has changed from a file to a box and has moved to the top and a line of letters and numbers have appeared where the inbox usually is. Both have exact copies of my emails in them. This appeared yesterday for no reason. Mi have managed to delete the lettered and numbered file and moved the inbox back to it's normal position but the symbol beside it still resembles a cardboard box unlike the rest of the files. Has anyone else experienced this or should I be worried. I have no idea how to change the symbol to the original file one and do I need to change it please, anyone? Thanks.

Pat