Electric.  Can be used with or without oil, which is pored into the glass top.  The heat from the bulb causes the oil to warm, sending out a heavenly sent that will fill an entire room. These are especially popular in bathrooms, but we also enjoy using them in the kitchen and bedroom.  Measures approximately 4" L x 4" W x 4 1/2" H.  Uses one Halogen Bulb, included.  Replacement bulbs are also offered for sale.