There are many types of wool/yarn that come in skeins or balls. These are big loops of yarn/wool that are brought in different weights and thickness. It is advisable to check the length and weight of wool/yarn that you buy against the ones used in the patterns to ensure that you have enough to finish your projects.
Lace wool/yarn (1-3ply)
(1-3ply) is a very fine wool/yarn that is used for more open patterns. They generally come in 50g ball or skein. Sometimes the lighter weight yarns can be doubled to create a more dense look.
Light worsted (DK/8-ply)
A medium thickness that is very versatile and suitable for many projects. This is the most popular weight of yarn.
Worsted (Aran/10 ply)
Is thicker than light worsted (DK/8-ply) yarn and will produce knitted items that are thicker than those made by other weights.
Bulky (chunky) and Super bulky (super chunky)
These weights of yarn are thicker, and work up more quickly than lighter weights of yarn and are ideal for bulkier projects.