Removed files on the left will be deleted on the right.  To disallow deleting, click this trash can.

To allow files that are removed on the left to be deleted on the right, click this trash can.

New files on the left will be created on the right.  To disallow creating, click this file icon.

To allow new files that appear on the left to be created on the right, click this file icon.

Changed files on the left will be copied to the right.  To disallow copying, click this arrow.

To allow changed files on the left to be copied to the right, click this arrow.

Removed files on the right will be deleted on the left.  To disallow deleting, click this trash can.

To allow files that are removed on the right to be deleted on the left, click this trash can.

New files on the right will be created on the left.  To disallow creating, click this file icon.

To allow new files that appear on the right to be created on the left, click this file icon.

Changed files on the right will be copied to the left.  To disallow copying, click this arrow.

To allow changed files on the right to be copied to the left, click this arrow.