The filters allow you to sync a subset of the concerned information type to
your device. If any information type is not fulfilling the criteria chosen
and is present on the device, then it will be moved to the computer and not
made available on the device. When syncing with two computers, it follows
the same logic on both computers.
A common issue most users face is that they would like to sync Personal and
Business category contacts from their Home PC but would like to sync only
the Business ones at Work. Unfortunately, this is not possible due to the
logic that the filter setup follows in ActiveSync.
For Example: If you were to setup the Home PC to sync the above two
categories, you will have contacts that satisfy both the condition on your
device. At work, if you set the ActiveSync filter to only Business, then
the Personal contacts will be sync'd to your Work computer but removed from
the mobile device (since it doesn't satisfy the condition on your Work PC)
and contacts having Business category on both devices will be synchronized.
The logic is same for Calendar sync as well.
Hope it addresses your query. Any particular reason you are interested in
knowing how it works?
Microsoft MVP - Mobile Devices