I think it's time to explain some of the terms I've been rattling on about (and will rattle on about in the future). Let's follow the whole process. First, part your fibre from the animal, this is either done by shearing or plucking, depending on the creature. Originally, sheep shed their fleeces themselves, much as a dog molts. However, wool used to be extremely valuable and people found it inconvenient to have to pick their wool out of the hedge so over years we bred the ability to shed their fleece out of sheep. This is why sheep have to be shorn, we humans have made sheep dependent on us. Alpacas and angora goats have the same problem, they also have to be shorn. Angora rabbits however do molt and can either be plucked when their coat is being shed naturally or they can be shorn. The best time to sort fibre is as it comes off the animal, this is the only time you can be sure which bit of the animal the fibre came from. Fibre quality varies depending on where it grew, and who wants to wear an animal's pubes anyway?
Once the fibre has been harvested and sorted, as a handspinner I have two choices, to wash the fibre first or to spin 'in the grease' and wash the completed yarn. I usually spin alpaca in it's raw state as alpaca is not very greasy and can become matted during washing. Angora goats smell terribly so I always wash mohair (mohair fibre comes from the angora goat, angora fibre grows on angora rabbits - confusing). With wool it depends on the project and the fleece, I have some very short eight week old lambswool I'm spinning in the grease because I reasoned the lambs couldn't have got that dirty in eight weeks and I was worried about washing the fibre. Saying that, I've helped out at lambing time and the amount of blood, birth fluid and mum's saliva lambs are drenched in the wool is probably far from clean!
The next step is to card or comb the fibre. Carding and combing are two different processes, carding is usually best for shorter fibres while combing is only suitable for long strong fibres. I have never used hand combs (it's an ambition of mine to learn to use them) so I will concentrate on carding. Carding can be done with hand carders or a drum carder. Basically a carder is a surface covered in teeth , rather like a fierce hairbrush, which separates out the fibres. Yarns insulate by trapping air between the fibres, carding helps to introduce air prior to spinning.
Technically there are two types of spinning: woollen and worsted. There are different processes for making a woollen yarn and a worsted yarn. However many handspinners, myself included, produce yarn which is a hybrid, not a true woollen or true worsted. A true woollen yarn is made from shorter fibres which are carded not combed and spun from a rolag using the long draw technique. A worsted yarn is made from long fibres which are combed and spun using short draw. I may mix these techniques up so I might card the fibre then spin short draw, for instance. A rolag is made when you remove the fibre from the carders and roll the fibre into a tube then spin from the tube. Rolags are generally spun long draw, in long draw spinning the fibres lay at right angles to the direction of the yarn, with short draw, the fibres lie parallel with the direction of the yarn. Woollen spun yarns contain more air and tend to have a fluffier finish, yarns which have been spun using short draw contain less air but tend to be stronger. A true worsted yarn will be smooth and strong with a good lustre.
To create a yarn, you can spin a single strand or ply several strands together. Plying makes the yarn stronger and creates a balanced yarn which will not distort the garment when knitted. A single yarn can be inclined to twist up on itself, therefore the danger is it will pull any garment made from it out of shape.
When the yarn is finished, it is best to wash the yarn to set the twist, washing helps to stabilise the yarn. I hang up the skein dripping wet, the weight of the water helps to remove any kinks.
I hope this brief explanation of spinning makes sense. Having written this, I think it is much easier to spin than to explain how it's done! Do ask questions if there is anything you would like to know more about.