What does Other mean when syncing an iphone?

When syncing my iPhone I notice that the a large part of my space is taken up by a block called other.

What is this made up of and How can try to make is take up less space?

I have this problem as well (3.2GB worth of it). I heard it consists mainly of old app data, corrupted data, album artwork, apps not deleting properly, app updates, calendar data, settings etc.

The only way I know of clearing it is using the clear and restore factory settings functions to, in effect, make your phone completely new again as far as software goes. You'd then have to resync everything though, but you should have less "other" space taken up. Do not restore from backup, as this will put on the "other" data again.