What are the types of elastic?
Braided elastic is probably what most of us think of when picturing elastic. It has parallel ribs going along the length of the elastic and it narrows when stretched. It also loses. its stretch when pierced with a needle, so it's not the best choice for sewing through. Braided elastic is commonly used inside casings, such as the necklines shown in the dresses at the top of this post, or in sleeve hems.
Fold Over Elastic
Fold-over elastic (commonly called FOE) is a great way to finish edges on stretch fabrics or garments where you want a smooth close fit that still retains the stretch. It is a great choice for underwear or athletic apparel, or even any clothing using knit fabrics. It is plushy on one side and smooth or possibly a print on the other so you can choose which side goes on the outside. It comes in a lot of colors and patterns, although some of the patterned FOE's can be a bit scratchy against the skin — such as the metallic one shown above — so be careful where and what type of garment to use those on.
Knit elastic can be applied directly to the fabric as shown above, or can be used in a casing as well. Knit elastic is a great choice for pajama pants or other applications where the elastic touches the body.
Elastic for lingerie is a subcategory in the elastic world. Most commonly knit elastic, it comes in a lot of different colors and textures and is designed for bras, undies and lingerie. This elastic can have a decorative edge, possibly scalloped or with a picot trim and elevates your creation from plain to pretty. Many of these elastics have a plush side for comfort against the skin. If you're feeling creative you could use them as a design element on the outside of a garment.