What is the ~ in the Sketchup file name?

Even when my files are closed and I’ve quit sketchup, my file names have a ~ at the end (no .skp extension). For example, I have a file named “Filename.skp” and then a second one that’s “Filename~”. I’ve looked around the web and found nothing on this. Does this mean my files are not closed properly? They still seem to function when I open them, but It just bothers me to have extra files. What are these files?

it’s your Backup copy, you must have it set in Preferences


Thanks for the clarification! Much appreciated.