RSU stands for restricted stock unit...seems like the OP was not at all confused about the terminology.
Of course RSUs stand for "restricted stock units", but they are very different from "restricted stock". This is really a case of an "unknown unknown". OP was not confused because OP did not know these were different things. However, as OP searches the internet to learn more about the tax properties of these instruments, she or he might not even realise that material that discusses "restricted stock" is discussing something completely different from "restricted stock units", and therefore it is very useful to point out that difference, as I have done in several threads. I speak from experience here; that distinction has confused
me in the past.
For example, various IRS publications discuss making an election to include restricted stock in income when it is granted rather than when it vests pursuant to 26 USC § 83(b) and subject to the conditions stated therein. This election is available for restricted stock but
not for RSUs. There are many other differences between these instruments. It is worth understanding that they are different so as not to be confused when researching this further.
Furthermore, even if OP was already aware that these two things were different, my post may still help other readers who were not aware of that. That said, I don't think OP was aware that an RSU is just a promise to pay an amount in the future, or she or he probably would not have posted this thread, since the tax treatment is the same as a cash bonus and is not novel. Of course, there's nothing wrong with not knowing that; this forum is a place to learn about such things. I am just contending that I did in fact provide useful information.