Shallots and onions you eat the bulbs. Scallions don't form bulbs but are pulled and both white and green top are eaten. Chives and garlic chives you eat the greenery which can be clipped and will grow back. The last two can be left in place for years and will produce more or less continuously during the growing season. Chive blossoms can be used to flavor vinegar (and turn it pink). They are very decorative as are garlic chives so both can be used in the flower garden.

Thanks, that is just the kind of answer I needed.