When purchasing yarn, you may find that it is twisted into a hank or skein. This is not ideal for working with the yarn for knitting and crochet projects. This is where a ball winder & swift are excellent tools to make a ball out of yarn that sits nicely and moves without effort as you work.
If you purchase yarn at your local yarn shop, they will likely have one that they can teach you how to use. If this is not an option, a ball winder & umbrella swift are must-haves for your craft tool-kit. A wood swift costs a bit more than the plastic + metal models but are less likely to catch your yarn as you spin the umbrella swift around.
An umbrella swift has the advantage of fitting perfectly inside the skein, regardless of the diameter. The amish table swift is typically limited to 4-6 sizes, which may not be a problem for your needs.