The Edit menu's Revert to Editing State will restore the metadata in the current file selection to the metadata snapshot automatically taken when the selection was made (or manually saved).
The Edit menu's Update Editing State command will manually take a new snapshot of the metadata.
The Edit menu's Exchange Current and Editing States does as the name implies. The current values becomes a copy of the editing values and the editing values become a copy of the current values.
The Edit menu's Copy Initial State to Editing State sets the editing state to be a copy of the initial values.