Fedora Magazine states in " How to rebase to Fedora Linux 35 on Silverblue":
Prior to actually doing the rebase to Fedora Linux 35, you should apply any pending updates. Enter the following in the terminal:
$ rpm-ostree update
And in " Updates, Upgrades & Rollbacks":
Once an update is ready, it is just a matter of rebooting to start using the new version. There is no waiting for the update to be installed during this reboot.
If you’d prefer, it is also possible to update using the command line. To do this, run:
$ rpm-ostree upgrade
But I could not find any reference in the man page to a
rpm-ostree update command, only to a
rpm-ostree upgrade one
Hence: What difference between rpm-ostree update and rpm-ostree upgrade in Fedora Silverblue ?