If you have set up a synchronization relationship between your mobile device and PC, synchronization keeps information up-to-date on both computers. ActiveSync synchronizes a limited amount of information by default to save storage space on your device. You can change the amount of information synchronized for a given information type in Settings for the information type.
Note Information stored on a storage card will not be synchronized with your PC.
See also
Overview of ActiveSync file conversion
Changing how much information is synchronized
Overview of copying and moving files
Change the synchronization schedule
Managing wireless synchronization costs