Knitting is a funny business. On the one hand, it’s remarkably simple - drawing loops of wool through other loops of wool to make a fabric. On the other hand, it’s remarkably flexible, and can be made to very complex things.
It’s a skill that lots of people all over the world have, and a skill that can be communicated. Person A can make a thing, describe to person B what they did, and then person B can produce a nearly-identical object without having seen the original. Person A can also teach person C how to acquire the skill.
Now, the thing about teaching people a skill like this, is that there are different ways to pull loops of wool through loops of wool while still getting the same result.* You can explain e-x-a-c-t-l-y how you do each individual action according to your method, with the learner trying to do e-x-a-c-t-l-y the same. Or you can explain the principles of the thing, and then the learner, understanding the nuts-and-bolts of how it all hangs together, can reproduce it in any way they choose. In reality, it’s usually a mixture of the two.
The first method is intellectually simpler - teacher and learner can happily know that it works but not know why. And there’s no necessarily anything wrong in that, right up until the point that a view develops that this one way of doing it is the *right* way and that the other methods are *wrong*. I might be a bit touchy on this subject as my way of knitting, which I love (continental combined, if you’re asking), is not the classical way in the UK…
Anyway, the point is that everyone doing the same is all well and good, comforting and tribal, but teaching people to understand how what they’re doing works possibly enables them to do more exciting things in the future.
Here comes the technical knitting example, focussing on which way round your stitches sit on the knitting needle.
Normal, correct, straight-down-the-lines, how-the-English-books-teach-it knitting looks a bit like this:
See how the knitting is made of little open n or u shapes, and the leg of the stitch nearer the right-hand tip of the needle is in front of the needle.
Now, if you wrap the wool round the needle the other way, your stitches on the needle will be the other way round. The stitches are ‘twisted’ on the needle:
Note, however, that the knitting below is still all open u/n shapes.
If you’ve learnt that you always knit through the front leg of the stitch, and you try to knit like that through these ‘twisted’ stitches (maybe you made a mistake on the last row, and accidentally wrapped the wool the wrong way: you don’t know you’ve done something different, and you don’t know that your stitches are twisted on the needle), you’ll end up with twisted stitches in the fabric itself. See how the wool crosses over itself in the loops:
This makes the fabric tighter, and will make YOs small and tight. If what you’re looking for is normal stocking stitch knitting like above, then it is wrong. But that doesn’t mean that whatever you did on the previous row has to be wrong - because as long as you’re on top of what you’re doing you can still make untwisted stitches on this row.
One way is to take each stitch and turn it round before you knit it. This is slow and tedious (although sometimes necessary for more complicated patterns). Or, you can just knit into the other leg of the stitch.
In fact, the general rule I follow is to knit (or purl) into whichever leg of the stitch is nearer to the end of the needle, rather than to always knit into the front leg. That way it doesn’t matter what you did on the previous row - you just knit each stitch as it comes along, always through the leg nearer the end of the needle. NB if you’re doing decreases things get more complicated, and an easy general rule is just to turn the stitches round so that they’re the ‘right’ way round.
If you want to twist your stitches on purpose, then you knit through the leg further from from tip. Simples!
ETA: for a whole world of knitting tips, tricks, and explanations (which really amazing drawings), see http://techknitting.blogspot.co.uk/.
* For example, you can hold your working needle in your right hand or your left hand (right-handed vs left-handed knitting). You can hold your wool in the same hand as your working needle or not (English vs continental knitting). Or you can wrap your wool one way or the other way round your working needle. That’s what I’m talking about here.