Q: what is other when syncing?

A  ' Large Other ' usually indicates Corrupt Data...

First Try a Restore from Backup... But... if the Large Other Persists, that is an Indicator of Corrupt Data in the Backup... Then a Restore as New is the way to go...

Details Here  >  http://support.apple.com/kb/HT1414

How Do I Get Rid Of The “Other” Data Stored On My iPad Or iPhone?

http://tinyurl.com/85w6xwn

With an iOS device, the “Other” space in iTunes is used to store things like documents, settings, caches, and a few other important items. If you sync lots of documents to apps like GoodReader, DropCopy, or anything else that reads external files, your storage use can skyrocket. With iOS 5, you can see exactly which applications are taking up the most space. Just head to Settings > General > Usage, and tap the button labeled Show All Apps. The storage section will show you the app and how much storage space it is taking up. Tap on the app name to get a description of the additional storage space being used by the app’s documents and data. You can remove the storage-hogging application and all of its data directly from this screen, or manually remove the data by opening the app. Some applications, especially those designed by Apple, will allow you to remove stored data by swiping from left to right on the item to reveal a Delete button.

 Cheers, Tom

I had 30GB of 'other' on my iPad, and tried a number of suggestions to remove it, but none worked. The only way that worked for me was:

1. Backup the iPad to iCloud or your Mac via iTunes.

2. In the iPad, go to Settings > General > Reset > Erase All Content and Settings and follow the prompts

3. When the iPad restarts, follow the prompts for language and country, then select the option to Restore from Backup, and choose the recent backup fro iCloud or Mac (in 1 above).

This will remove, or at least reduce, the 'other' space back to under 1GB.