Pillar: A thick candle with a geometrical cross section such as a circle, oval, or hexagon is called a pillar. It is usually referred to by its diameter followed by its height. For example, a 3-by 6-inch pillar would be 3 inches in diameter and 6 inches high. Some pillars come in standard sized for commercial and religious use but you can make many variations of pillars by using molds.

Novelty: These are irregularly shaped candles made by molding, sculpting and/or pouring.

Taper: These are the long cylindrical candles that kindle memories of historic candle-dipping. Tapers can be made by dipping wicks into melted wax, by pouring wax into a mold, and by rolling wax around a wick. No matter the method, the result is always candles made to fit into a holder.
Tapers are generally made 1/2 inch or 7/8 inch in diameter at the base because most holders are designed to fit these two sizes. There are, of course, exceptions, such as birthday candles (3/16 inch) and Danish tapers (1/4 inch). Some specialty candleholders are designed to hold a taper larger than 7/8 inch.

Votive and Tea Lights: Although these candles originated in the church, the term now refers to small plug-type candles that are 1 1/2 inches in diameter by 2 to 3 inches high. This shape has become popular for scented candles because their small size allows them to fit easily into small rooms, such as bathrooms.
As votives melt and become liquid in their containers, the wick uses up all the liquid fuel. If you burn a votive on a plate, the burn time will be shorter because the wax will drip and the wick will be unable to use it.
Tea lights are small votives used to warm pots of potpourri and to heat foods. They fit in smaller-than-standard votive cups.