Shellac by CND is a specific brand of gel nail polish. All Shellac brand polishes are gel nail polish, but not all gel nail polishes are Shellac.
Gel nails refer to a type of manicure in which a layer of polymer resin, or gel, is applied to the natural nail and allowed to harden under an ultraviolet light. Depending on the brand, the formula may show varying degrees of strength and flexibility. In some cases, the gel layer may be thick enough to serve as an artificial nail that can be extended past the natural nail and filed into shape. In other cases, it is simply a protective top layer over colored polish or a natural nail. A gel overlay refers to a clear or lightly tinted layer applied over the top of color, artificial nail tips or natural nails. It has the appearance and functionality of top coat and can be used in conjunction with traditional nail polishes.
The brand Shellac is manufactured by the polish company CND and is of the type of gel that is blended with colored polish and applied in a single step. It is generally opaque and replaces the need to apply color underneath. Shellac is one of the thinner gel formulas on the market and requires less effort to remove. It is not substantial enough to be formed into an artificial nail extension.