Pearl onions are tiny white, dried onions (about 1/2" or less in diameter) used in a variety of stews, soups, and meat dishes. Pearl onions are smaller than boiling onions. These little onions are notoriously difficult to peel. The onions can be find in white or red.
In addition to being used in cooking the onions are pickled and sold in jars. This is the traditional garnish for the Gibson cocktail or a substitute for an olive in a martini. Another popular dish using the onion was pearl onions in a cream sauce or pearl onions and green peas.
These are typically found in small net bags in the produce section of most well-stocked grocery stores. Some stores sell frozen, peeled onions which are very convenient.
The easiest peeling method is to drop them into a small pot of boiling water for about 30 seconds then transfer them to a bowl of water with ice. The outer skins will be easier to remove.