Gel can mean lots of things. The main characteristics are a thicker consistency and UV light curing instead of drying. Gels can be similar to traditional polishes or thicker, stronger and longer lasting enhancements. Some gels, often just called "gel nails" in quickie salons, are acrylic that uses a gel and powder combo instead of liquid and powder. Some gels contain antimycotic elements and are used to rebuild damaged toe nails, while preventing nail fungus.
Shellac is a "power polish" created by CND. It is essentially a gel polish, but has some properties of traditional polishes, including some solvents that will evaporate as it dries. It cures in a UV lamp in two minutes per layer, except base, which is ten seconds. You will not smear or damage it. It is thin on the nail, lends a small amount of structural support to weak nails, and is soaked off in 8 minutes with CND's Nourishing Remover.
Shellac is fairly sticky and lends itself well to techniques that utilize it's stickiness, such as adding pigments, glitter fades, stamps and foils. It is also good for laying stickers into. However, it does not blend very well, so gradations, or fades, are best done with glitters and pigments, rather than the polish itself.
Gelish is a gel polish, and is very similar to Shellac. One key difference is the non-porous topcoat. It is more resistant to staining and chemical exposure, and it will not accidentally soak off with exposure to acetone. In order to remove it, one must file through the topcoat with a file or buffer to allow the acetone to penetrate into the color and base coats. Another difference is that it cures in either a UV lamp (compact fluorescent bulbs) or an LED lamp (still UV spectrum). LED lamps are much faster than UV, curing most color coats in 30 seconds rather than two minutes. It is thin on the nail, lends a small amount of structural support to weak nails, and is soaked off in about ten minutes using Gelish Remover.
In terms of art, Gelish is great for blending and mixing, as the layers can be quite thin, and colors can be mixed before curing. It lends itself well to gradations, otherwise known as fades or ombré. It is reasonably good for placing glitter and other additives as well as stickers.
Bio Sculpture Gel (BSG) is a soak off, or soft, gel that is thicker than the polishes, although it can be applied fairly thinly. It is UV or LED cured. Being thicker, it is appropriate for correcting irregularly shaped nails and adding length. Length can be added with glue on tips and reinforced with gel, but I typically will sculpt the extension on a form, creating a thinner, more natural feeling nail. The gel has a similar flexibility to the natural nail, so it will absorb impact rather than transferring it into the nail plate, as can happen with more rigid nail enhancements, such as acrylic. BSG is a soak off gel, and can be either filled at each appointment or soaked off like the polishes.
As a thicker gel, BSG lends itself to more intricate art, 3D techniques, and gem placement. It is great for encasing stickers without lifting or peeling. Crystals will typically stick around the entire time between services. 3D shape , such as bows, flowers, and animals, can be sculpted directly on the nail. Serious glitter can be embedded with a smooth finished surface.
Akzentz is a hard gel, which means it is non-removable. Typically, a base layer of clear gel is applied to the nail, forming a buffer for future work. Color and art is layered on top of this cushion. At the next appointment, which is typically 3-4 weeks, the color will be filed off, leaving the clear cushion. The new growth is filled with clear, and the color is reapplied. This system allows the nail to only be touched once, and is therefore very gentle. It is best for clients who know they will always get their nails done regularly. If the client does decide to "remove" their hard gel, it is filed very thinly and allowed to grow out. As it is clear, this is mostly unnoticeable and can be further hidden with any type of polish.
Like Bio Sculpture Gel, Akzentz can be used to correct shape and add length. It can be used to create 3D shapes, although many of the colors I carry are in their Luxio line, which is a polish style gel with amazing pigmentation that cannot be used to create 3D shapes.
Appropriate art styles include more intricate art, 3D techniques, and gem placement. It is great for encasing stickers without lifting or peeling. Crystals will typically stick around the entire time between services. 3D shapes, such as bows, flowers, and animals, can be sculpted directly on the nail. Serious glitter can be embedded with a smooth finished surface.