Why are there spinning arrows next to a disc in a Finder window?
I use a 2TB external drive for backup with Time Machine. It is always connected to my iMac (OS 11.2). I do a manual backup every night before I go to bed. I've noticed that spinning arrows are displayed next to the name of that disc in a Finder window in the morning when I get on the computer, which is never turned off. Time Machine indicates that the backup finished shortly after it started, which is normal. What's going on and what does that indicate?
iMac 27″, macOS 11.2