Exclamation Points and check marks on the file icons?

I dont know why all of the file icons like doc, mp3, jpg, etc; have either a green circle with a check mark or a red circle with an exclamation point at the bottom left corner of the icon. I am not able to figure out what this means. What is wrong with this files that have red exclamation points? Each of them are opening properly but I dont really know why this icons have turned up wrong? Thanks for any replies.

Did you recently subscribe to an online backup service or you had recently installed backup software on your computer? Normally, the online backup services and some backup programs use small icons to mark files that are backed up with those that have not yet been backed up, your case might be similar to those.