Edit -> Copy files on MacBook and message appears on my iMac???

Hello,

I purchased a new MacBook Air M1 and I just noticed something I never did before.

If I select a bunch of file top copy from the finder "Edit -> Copy" on my MacBook Air M1, I see a message on my iMac computer that says copying files from MacBook....etc.

What feature is this? Is it copying files from my MacBook Air to my iMac? I was just copying files from my MacBook Air to paste into a folder of a flash drive.

Thanks!