This kind of range is similar to its smaller cousin, the hot plate, but is designed to hold much larger cookware and have higher heating power. You can get one with single or double burners. All of the units have 18 inch burner grates, so they're bigger than the burners on standard gas ranges. These are especially rugged, because the items they support can be very heavy - a full 100-quart stock pot can weigh up to 200 pounds. Heavy-gauge steel legs are designed to support the weight. If you're not going to be heating large stock pots, or you need an electrically-powered option, one of these is probably overkill.
The grate is the part of the range that the pot sits on, and all of the ones you'll find here are cast iron. Cast iron is valued for its durability; it is resistant to breaking, scratching and chipping, and can handle lots of repeated use and abuse. Also, cast iron retains heat better than other common materials like steel, so when you put a pot on, it'll stay hot even as heat is absorbed into the cookware. This means you can cook faster. Another perk is that the grates are fully removable, so when it's time to clean your equipment, you can do so quickly and thoroughly.
You'll notice that many of these units will have two knobs to control the heat, even if they just have one burner. That's because the burner is made up of two rings, one inside the other, and each can be operated independently. This means that one ring can be left off if you need low temperatures, for holding dishes at serving temperature, for example. For simmering or bringing food to a full boil, both rings can be turned on. Dual controls give you more precision control than one alone and they're also more energy-efficient.
BTU stands for British thermal unit, a measurement commonly used for heat output. Paying attention to the BTU of a stock pot burner can be a good way to compare the power of each unit when you're shopping. The most common amount is 90,000 BTUs, or three times the power of an ordinary gas burner. Many models offer more than 100,000 BTUs and some even top 200,000.
A lot of these have compartments underneath the burner that you can use for storage. Since the equipment is designed to be at a comfortable working height, these compartments are designed to utilize the space beneath the cooktop so you can keep items you'll want on hand when you're cooking. You can easily store pots, pans, and spices.