Bias trim is a type of flat trim that is cut from fabric on that fabric’s bias.
Because it’s cut on the bias, bias trim has more stretch to it than regular woven trims, which means it can bind the edges of garments or upholstery items with curved edges. It’s also sometimes used inside a garment, to help reinforce a seam.
You can buy pre-cut bias tape at any fabric store, but it’ll be a very dull cotton/poly mix. It’s not very interesting to look at, but it IS easy to sew. If you need something with more zing, you can cut your own from any fabric – although bear it mind how challenging it might be to sew when you use it. You don’t want to make bias trim out of silk charmeuse, for instance. But it’s possible that you’ll want a nice satin bias to finish the edges of your steampunk corset, in which case, making your own might be the way to go.
Store-bought cotton-poly trim is machine washable and can go through the dryer on low. The washability of home-made will depend on your source fabric.