There are over 1000 different varieties of onions ranging from subtle and sweet to sharp and pungent.
There are 2 categories of dry onions, storage and sweet. Storage onions, better known as yellow, white and red onions which are firm, have thick papery skin and last for months from harvest.
Sweet onions such as Vidalia, Walla and Maui are softer to the touch and best refrigerated. These onions are milder than storage onions but will not last as long.
And, there a green onions, such as scallions, welsh and chives, all of which need to be refrigerated.
The following are a list of onions and their various uses:
Vidalia: sweet and mild, use raw or cooked; in salads or sandwiches, grilled and in chutneys or relishes.
Red: slightly sweet, may be used raw or cooked; good on turkey or veggie burgers and salads
Shallot: garlic like, sweet and delicate, works well in sauces and salad dressings.
Pearl (Red and White): flavor varies by variety; milder and more delicate than mature onions, good uses: on kebabs, for pickling or roasting whole
Welsh: bright, tangy and sharp, works well when served raw or adding in the last few mins of cooking: perfect for finishing and garnishing; brushed with olive oil and grilled whole, also Asian cuisine.
Yellow: Strong pungent flavor and aroma; most versatile; best when cooked, very strong when raw; considered classic onion flavor. This onion works well in soups, stews, braises, grated in burgers, stir-frys and diced in stuffing.
White: milder and sweeter than the yellow onion, may be used raw or cooked; good in stir-frys, salsas, sandwiches or stews, in spicy dishes to sweetness, in particular Mexican cuisine.