There is an old phrase.
"What’s the difference between a regular priest and a monsignor?"
Answer: "None, though most monsignors forget that.
Well… there are monsignors and there are monsignors. It is both a church honor given to some priests and a title applied more broadly.
Check out Shouts and Fr. Selvester’s good posts on "monsignors" and ecclesiastical heraldry.
Here is a tease.