Chives Have a mild onion flavor and make a nice garnish.
Leeks Have a mellow onion flavor and can be used interchangeably with onions.
Green onions Also are known as scallions and usually have a mildly pungent flavor.
Yellow onions Can be round or flattened; sweet varieties include Vidalia, Walla Walla, and Maui, which are great for caramelizing.
White onions Often have a sharp flavor; smaller varieties include pearl onions, about 1/2-inch in diameter, and boiling onions, 7/8 to 1-1/2 inches in diameter.
Shallots Have a mild, delicate flavor that is outstanding when added to sauces.
Red onions Generally have a sharp flavor. They are valued for their color when served raw.
Garlic Is strongly scented and pungent. Elephant garlic is larger, milder, and more closely related to a leek.