"Refresh" vs "Auto-refresh" in `snap changes` output

I just ran snap changes and saw the the core snap was "Refresh"ed and the multipass snap was "Auto-refresh"ed:

ID   Status  Spawn                 Ready                 Summary
186  Done    2018-02-21T19:37:31Z  2018-02-21T19:37:56Z  Refresh snap "core"
187  Done    2018-02-22T15:30:09Z  2018-02-22T15:34:22Z  Auto-refresh snap "multipass"

What’s the difference here?

The Refresh snap "core" message is created to describe the change when the you do, for example, snap refresh (or also snap refresh core foo bar; anything other than just one).

If you’d done snap refresh core, the message you’d see would be Refresh "core" snap.

The Auto-refresh snap … message comes from snapd itself, doing a periodic refresh and finding it can refresh something.

There’s a fourth one, but there’s a bug that makes it look like the first one, which is what you’re seeing here. That’s the fallback systemd timer prodding systemd in case the internal timer got stuck.