Excuse me, are researchers in American universities permanent or temporary positions (Stanford's)?

It depends on your contract ... scientific research is linked to the professor's laboratory. I think you are a science/engineering major.

So if you look at the job advertisement, it usually says' this position is a two-year contract', so it is a two-year contract, or' this is a long-term $ TERM/ permanent position', so it is fixed. Usually the former. As long as a certain amount of time.

Generally speaking, it is temporary for professors to recruit postdocs, as long as you have n years. Internally (for example, I am doing RA for a professor now), I can stay after graduation, which is also a hint. You only stay for a short time of one or two years.

Generally speaking, in a laboratory, the professor's head is always there, and then there are a bunch of postdoctoral fellows (usually 2 years), visiting scholars (usually 1 year), graduate students (until graduation) and undergraduates (you can stay for another year after graduation, but it is not good to stay any longer). These are all research, except that the boss is short-term. These staff are permanent.

Staff scientists are permanent, but that is linked with a research institution, but that institution is near the university.

The most important thing is to look at the job advertisements. People write very clearly.