Thumbnails

Before I saw the 57 slides, I had thought that a thumbnail was a folder which kept pictures, but now I know that it is actually a small photo which is used to speed up the time it takes to display the photo. I stumbled across this when I was using an app called Clean Master to clean the junk from my phone, and it asked me if I wanted to delete my useless thumbnails, so I pressed yes. However, I noticed nothing gone after that so I found it weird.