Shallots are thought to have originated in Asia and traveled through India and to the Mideast. They are known botanically as Allium ascalonicum, derived from Ascalon, a coastal city in Israel where they were cultivated. The Crusaders brought them to Europe and it is thought that De Soto brought shallots to the United States during his Louisiana explorations.
Shallots are a member of the same families as garlic and onions. They have a mild flavor, a bit like a sweet onion with a hint of garlic. They are covered with an onion-like papery skin but have multiple cloves like garlic. When a recipe calls for a shallot, it means the whole shallot, not just a single clove.
A colleague credits Anthony Bourdain for stating that the shallot was the difference between restaurant food and home cooking.