Partially Downloaded Files Extensions - What are partiallydownloaded files and how do I open a partiallydownloaded file?

What are partiallydownloaded files and how do I open a partiallydownloaded file?

File Type Category File Format
.!bt Partially Downloaded Files BitTorrent Incomplete Download File
.!ut Partially Downloaded Files uTorrent Incomplete Download
.desktop Partially Downloaded Files Desktop Entry File