Lox is traditionally a salt-cured fillet from the salmon's belly, an area with the fattiest and richest meat (similar to a pork belly). If you've never had it with a bagel and cream cheese (or a bagel and "schmear"), then you're seriously missing out. Nowadays, the terms "lox" and "smoked salmon" get used interchangeably, so check that you are getting the real thing if you buy lox from anywhere beside an in-the-know deli. F&W's guide has tons of recipes to satisfy your lox cravings.