Most Xeons are just server/workstation versions of their desktop counterparts with two major differences:
1. Particular features for multi-processor configurations (not multi-core, multi-physical processor)
2. More stability. For example, a 2.4GHz Nehalem Xeon might use the same grade of silicon as a 3GHz i7. It only really matters for overclocking.
Some Xeons use different sockets than Intel's desktop lineup, but these are usually specifically meant for multi-processor server configurations, since their compatible motherboards don't have the same feature set as a usual desktop motherboard (eg. limited graphics upgradeability and 12 RAM slots.)