You will see special icons on your files when accessing your mounted disks in File Explorer. They are there to quickly inform you of the status of your uploads.

There are 3 icons available and their meaning is as follows:

cm-status-icon-downloadThe file is being downloaded.
cm-status-icon-uploadThe file is being uploaded.
The file could not be downloaded or uploaded because of an error. This often occurs when you have reached your storage limit (can't upload), run out of space on your hard drive (can't download), or experienced network problems.