A tealight, or nightlight, is a candle in a thin metal or plastic cup so that the candle can liquefy completely while lit. They are typically small, circular, wider than their height and inexpensive. Because of their small size and low level of light, multiple tealights are often burned simultaneously. (Wikipedia)
Tealights derive their name from their use in teapot warmers, but are also used as food warmers in general, e.g. fondue. They are a popular choice for votive candles.