The process of establishing consistency among data from a source to a target data storage.
Data synchronization is the process of establishing consistency among data from a source to a target data storage and vice versa and the continuous harmonization of the data over time. It is fundamental to a wide variety of applications, including file synchronization and mobile device synchronization.
Questions having the sync regards data synchronization between the Windows Phone 7 device and a target data storage, like Zune.
Reference: http://en.wikipedia.org/wiki/Data_synchronization