A nightlight is a small, low-powered electrical light source placed for comfort or convenience in indoor areas that become dark at night.

• Before they were powered electrically, nightlights were usually long-burning candles placed in fireproof metal cups, known as tealights in some countries. (Tealights in the U.S. refer to very short and wide candles that can be purchased within or without an aluminum tin cup that are commonly used inside a decorative glass holder.  They are also known as votive candles.)
• There are roughly 90 million nightlights purchased each year in the United States. In 2001 alone, more than 600,000 of them were recalled by manufacturers for safety reasons.
• Defective nightlights can cause fires, burns and electrocutions.

(read full article on InterNACHI)