After running the command sudo apt update in the terminal on Zorin OS 17.3, I get an error related to the lock file /var/lib/apt/lists/lock, which appears to be held by the packagekitd process. What does this message mean, and what is the proper way to resolve this issue?
Do you have automatic Updates in the Software Updater and Gnome Software active? Like @Aravisian already explained. This can happen when more than one Process tries to run the Package Management.
Normally Waiting until the Process of one of them is finished, should solve it by its own.