EasySync has three modes of operation:
Sync. In sync mode, copies any unmatched files left to right and right to left. Files are never deleted from either the left or right folder
Clone. Makes the right folder identical to the left folder. The left folder is not changed. Files may be deleted from the right folder
SmartSync. SmartSync detects files that have been deleted from either folder since the last sync operation or the last time a snapshot was created, and mirrors these deletes to the opposite folder. New or changed files are synced normally. You can create a new snapshot from the Folder->Create SmartSync Snapshot menu item.