One-way sync

One-way sync makes a destination an exact mirror of a source. New and changed files are copied across — and files at the destination that aren't in the source are deleted. Changes made at the destination never flow back.

In Data Transfers this is the Sync (one-way) operation: "Make destination mirror source. Files in destination but not in source are deleted."

That last part is what sets it apart from Copy, which only ever adds and updates. Point a one-way sync at a folder that holds other things and they'll be removed. Try it first with Dry run to see exactly what would change.

If both places change and you want each to pick up the other's changes, that's two-way sync.

See also: Copy, Move, Sync or Two-way sync · Trying a transfer first with Dry run