1. In general, sync refers to an exchange between multiple devices or programs that makes the data on all devices identical. For example, you may use Google Chrome to share your bookmarks, passwords, and browser settings between multiple computers.
2. When referring to hardware, sync is a term used to describe the process of connecting a peripheral, such as a smartphone, to a computer. This process also involved updating any information that differs on either the two devices. Syncing keeps a devices's data backed up and up-to-date.
3. Sync is also used to describe Microsoft's Active Sync.
4. With Windows Sysinternals, Sync is a utility that flushes cached data to disk.