You can synchronize data between your iPhone and only one computer. If you have a laptop and a desktop computer, and each computer contains different music files and contact information, your iPhone can synchronize data with only one of them. If you try to synchronize with more than one computer, you'll risk losing all your iPhone data.
You can synchronize the following types of data:
Contacts and appointments
Safari browser bookmarks
When synchronizing data, select the type of data you want to synchronize (such as email), and then choose the specific data you want to transfer (such as email from a particular account). After you select everything you want to transfer, ...