The terms panel bed and platform bed can mean a few different things. They can refer to the overall look of the bed, the style of the headboard and footboard or the bed construction. You can take a look at all of these differentiations, but the reference to construction tends to be the most useful because it often indicates whether or not the bed calls for a box spring.
Which One Needs a Box Spring?
According to standard interpretation, a panel bed is designed for use with a box spring and mattress; a platform bed is meant for a mattress alone, because the platform can take the place of the box spring. But as you might guess, not all manufacturers and retailers follow this as a rule. The best way to determine whether a bed needs a box spring is to look at the frame structure. If it has a foundation made of closely spaced slats connecting the sides of the bed or of one or more solid panels (with or without ventilation holes), it should be used without a box spring. On the other hand, if it has rail-like supports along the sides of the bed frame and few or no supports across the middle, it's designed for a box spring. Box springs have their own support structure and need only small rails or channels along the edges to keep them off the floor.
Panel Vs. Platform Style
In very general terms, panel beds are often characterized as traditional in style, while platform beds are considered more modern. This distinction still has some merit, but the line is much more blurry than it used to be. Platform beds are epitomized by a low profile, horizontal lines and an overall minimalist aesthetic. When they first became popular, it was uncommon to have a bed with no box spring, and the low level and often simple decoration of these beds lent an undeniably modern look. Today, however, beds without box springs are more or less standard. Mattresses are not only better (and don't need the extra support or give of a box spring), they're also thicker, which can bring a platform bed closer to the height of an older traditional bed that has both a box spring and mattress.
Often the term "panel bed" is used to describe beds with a tall, panel-like headboard and footboard. A typical example also might be a bed made of natural wood that has traditional frame-and-panel styling, similar to a frame-and-panel door or wainscoting. These beds usually have wide side panels that partially or fully conceal the box spring. Of course, there are many exceptions, and you can find "panel beds" with headboards and footboards made of wood slats, metal rods, wicker, upholstery, or even rough-hewn logs.
A Platform Can Include Storage
One of the features you'll find more commonly on platform beds is built-in underbed storage. This is often in the form of drawers built into the platform base, but it can also be open cubbies or short bookshelves. The idea is that you're integrating bedroom furniture with the bed, as opposed to a standard bed frame that offers just a little space for sliding in some bins.
Why Use a Box Spring?
The point about mattresses is worth revisiting. Box springs are considered optional with most new mattresses, which are designed to be "one-sided," meaning you don't have to flip them periodically, like in the old days. So why would you want a box spring? There are two main reasons: Box springs create a taller bed, which is easier for many people to get in and out of, and they're still part of a traditional bed look. If you like a tall, luxurious bed with a full-size bedspread or a bed skirt touching the floor, a box spring gives you what you need. In some cases, there's also a third reason to use a box spring: Mattress warranties often require a foundation made of a box spring or a suitable platform bed to ensure adequate support for the mattress. If you don't have a good platform bed, you may need a box spring to maintain the warranty