...however you want to spell it; the places in Torah where the received tradition says we write one thing and read another.
I'm sure there are squillions of scholarly theories regarding these, knocking about. I've not read them. This is strictly experiential, from a scribal perspective. There is a gigantic table of them under the cut.
There are two of these in Torah. Euphemisms are easily understood - at some point, we decided that certain words were too rude to be read out loud in shul, so we substituted politer ones. From a scribal perspective, that's the end of the story, but it does raise the wider question of why it's okay to pretend the Torah says something it doesn't. I mean, we spend so much time insisting that every word is deeply significant; how is it okay to make these changes?
These are super-easy to understand. I've done most of them myself, except that when I do them they're errors to be corrected. When you write, you're looking at what you're writing, and holding the words in your head. Most people do that by saying the phrase to themselves, so it's easy enough to mix up lo-with-a-vav with lo-with-an-aleph. People with snapshot memories are at an advantage here, I suppose. I've listed six of these.
Missing yud - vav instead of yud-vav
I could have listed these as homophones, I suppose, but they're very specific - all instances where the word should finish yud-vav, with the sound "v," and have been written without the yud. This is understandable: you might have had "v" in your brain, and attached "vav" to that thought, and written that. This happens 13 times.
Hey instead of vav
Sometimes a hey at the end of a word carries the "o" sound, like in Shlomo (שלמה). So things like בְּעִירוֹ, which ought to have a vav on the end, could have בעירה substituted for them relatively easily, since they'd be homophones. I don't understand why this substitution might happen when the vav carries the "u" sound, though, unless the two used to sound the same. Anyway, there are seven of these.
There are plenty of places in Torah - words like חדש - which could perfectly plausibly be spelled with an extra vav, חודש. Rabbinic Judaism takes it for granted that whatever these may have been on Sinai, we've completely lost the tradition for when that happens, so we just do the best we can. We're not talking about those missing vavs here. These ones are stranger. There are three of these.
A yud where a vav ought to be, or a vav where a yud ought to be
There's a reason scribes are cautioned to be very careful about making their vavs sufficiently long and their yuds sufficiently short, and this is it. This is the most common sort of difference, there are 18 of them.
Jen hasn't the faintest
We insist that Torah is copied very carefully, from a copy, and proofread before use, and we insist that a Torah with a single error is removed from use until the error is fixed. I suspect this is basically how the text has managed to stay in pretty good shape over time. We don't have similar rules for the rest of the Bible, and those texts are far more corrupt. Apart from the euphemisms, the craziest Torah gets is a rogue letter here and there. Prophets and Writings have whole words doing crazy things, up to and including not even being there any more (so you write nothing, but read a word). This is a very nice example of how texts get more corrupt if you are less careful about their transmission.