In one sentence, describe what the following article is about:

As with most fruits and vegetables, there are many variations of the onion that are appealing for different reasons. Onions come in three general colors - white, yellow, and red/purple - each with their own distinct taste. Additionally, onions are categorized into two growing types: long-day and short-day. Long-day onions are named such because they begin sprouting when the days between 14 to 16 hours in length (late spring/summer), while short-day onions begin sprouting when days are between 10 to 12 hours in length (winter/early spring).  Long-day onions grow the best in northern states, while short-day onions grow the best in southern states.  Yellow onions are golden in color and have a slightly sweet flavor, white onions are sharp and a bit tangier than their yellow counterparts, and red onions are violet in color and are often eaten fresh rather than cooked. In general, there are two popular ways of growing onions: using either onion sets (bulbs) or using onion seeds. Gardeners tend to prefer planting onion sets, as they are a bit hardier and stand up to poor weather better than onion seeds. However, if you're able and willing to grow your onions from seeds indoors and transplant them outdoors, you can certainly raise them all on your own from seeds. You can also plant your onions in the ground in warm weather.  You can choose to grow onions from transplants/cuttings, but this isn't always successful and is much more difficult to accomplish than just using sets or seeds. Visit a local nursery to get recommendations on sets and seeds that grow well in your area. Onions can be tricky to grow if they're not planted at the right time. If planted in cold weather, they can die off or waste energy in blossoms rather than bulbs in the spring. If you're planting seeds, start them indoors at least 6 weeks prior to planting outdoors. Make sure that you sow the onions 6 weeks before your average last frost date, and set them out after that date. Onions aren't too terribly picky when it comes to growing conditions, but they do have some preferences. Select a place with plenty of room and full sunlight. Onions will grow quite large if they're given enough space, so keep in mind that the more area you give them to grow, the larger they will get. Avoid planting them in a location that is shaded by larger plants or trees. Onions grow well in raised beds, so if you're unable to find adequate garden space, you can build a separate raised bed for your onion crop. Although it takes some forethought, if you are able to prepare the soil of your plot for planting several months in advance, you'll receive a better onion crop down the line. If you're able, begin tilling the soil and adding in manure in the fall. If your soil is very rocky, sandy, or has lots of clay, mix in some potting soil to help even things out. Additionally, test the pH level of your soil and add in any necessary compounds in order to create a pH that falls between 6 to 7.5. Testing and altering the pH of your soil is best done at least a month prior to planting, so that any additives have time to take effect on the soil and prepare the foundation for the onions to grow.

Summary:
Choose a type of onion to grow. Decide how you will plant the onions. Know when to grow. Select the ideal location. Prepare the soil.