Electric fondue pots are self-heating. Other varieties require an external heat source, typically provided by a small can of Sterno or a candle. The candle or Sterno provides an open flame under the fondue pot. While electric fondue pots tend to be more convenient, in that they don't need to be periodically relit or replenished with a new candle or Sterno can, they are not as portable, and need to be close to an electrical outlet.
Sterno and Candle
Sterno is a brand name for a jelled alcohol substance that comes in a small can. When the user removes the can's lid and lights the top of the substance with a match, it ignites. It continues to burn until all the substance burns up, or the user places the lid back on the can, extinguishing the flame. Campers often use Sterno when cooking. Instead of a Sterno-like heat source, some fondue pots use small tea candles or larger votive candles.
Heat generated from a candle's flame is much less intense than heat from a can of Sterno. Some votive candle brands discourage the use of their candles with fondue pots. While heat from a candle flame might be sufficient to keep chocolate fondue warm, it won't generate enough heat to keep oil bubbly for cooking pieces of meat. Some small chocolate fondue pots are designed to use with tea candles or votive candles.
Heating and Cooking
You will usually need to initially heat a non-electric fondue pot over a stove burner. A candle won't get hot enough to cook or heat the contents of the fondue pot. While it is possible to cook and heat some foods with Sterno, consider the additional cost. It is possible to burn through several cans of Sterno before bringing the fondue to serving temperature. The purpose of the Sterno or candle is to maintain the heat in fondue cooking.