Wool: The most common type of yarn fiber out on the market. Very warm and durable, however it can be slightly itchy and is not the right yarn to use if the wearer has allergies to wool. It holds its shape well after blocking.
Merino Wool: Possibly my favourite yarn to use. Taken from the merino sheep, this yarn is super soft and doesn’t cause allergic reactions as regular wool does. Blocks very nicely but can “pill” (create little fuzz balls). If you get the chance to work with merino wool, do it.
Alpaca: Taken from alpacas, this yarn is warmer than wool, so this type of yarn is best for small winter projects. Doesn’t block as well as wool does but it is rather soft.
Cashmere: The softest and fluffiest yarn of them all, but is also rather expensive and not that strong.
Cotton: Not my favourite yarn to work with. While this is a strong yarn, it does not block well at all (it is a rather rigid yarn) and will highlight the irregularities in the stitches. However, it is light and breathable, so once you’ve gotten the hang of knitting, you can attempt to make summer garments.
Acrylic: Man-made fibers but is cheap and the best choice for beginner knitters. If you are planning on knitting something you know you have to wash regularly, this is the yarn to go for. However, once you’ve gotten a better hand on knitting, its best to move onto the natural fibers.
Silk: Expensive, but strong, shiny and lustrous. Its not the warmest yarn so it is best for summer projects. It is also slippery to work with, so hold off for a while before tackling a project using silk yarn.
There are many more yarn fibers that you can find at your Local Yarn Store (LYS). Additionally, there are balls of yarn that blend two or more fibers together. In general, these blends with give you the best of each fiber type, without their weaknesses. For example, one of my favourite blends is merino wool x silk, making for ridiculously soft and warm shawls.
It is important to note that using different yarn fibers with wield different results in your knitting project. If a pattern specifies what yarn to use, using the exact yarn or something similar in fiber content is best.
Yarns of different weights next to each other for comparison
Yarn weights refer to the yarn thickness. Knitting projects will call for a certain yarn thickness that you must use if you want your project to be the same dimensions and have a similar look to the final result. Check the yarn label for the weight, gauge and recommended needle size. Again, if you are buying yarn for a pre-made pattern, it is best to follow the directions.
Lace: (One of the) thinnest yarn you can get. This is used for light and airy shawls with lace patterns.
Fingering: Also commonly used for shawls, this weight is slightly thicker than lace. If you want your stitches to be fine, this is the weight to go for.
Sport (and DK): Twice as thick as fingering yarn, this is the most common yarn used for knitting socks!
Worsted (and Aran): The most common yarn weight for beginners to start with and possibly the best yarn to use for almost any project. Aran is slightly heavier than worsted, but both can be used in a variety of different projects.
Bulky (and Chunky): If you want to make something quickly, this is the yarn for you. The end result is bulky and chunky but makes for a warm cowl or scarf! Not for intricate patterns though, the yarn is too thick for that.
Standard yarn labeling chart from YarnStandards.com
This type of information will be available to you on yarn labels (though most don’t include the Symbol and Weight name). The most important areas to look at are: recommended needle size, gauge (the amount of stitches fit in 4 inches) and weight. Some yarn labels will only include the first two, because with both that information combined, you will be able to figure out what weight of yarn you are holding.