I just received an email form a new machine knitter asking about yarn weights and what is the best for her machine.
When I started machine knitting I had the same questions; do I use a 2 or a 3? Then with the fractions, example: 6/12 and etc. There is also the weights used in the U.K., example: 4-ply and use three ends, you get the idea. It can be a bit confusing.
Since I am here in the USA, here is a link to Angelika's website, she explains the US weights and also has the Yarn Council of America yarn weight symbols and what machine they work best on.
Angelika's Yarn Store