Research Scientist vs Staff Scientist in US academia
They could be anything and it will vary widely between institution. They may or may not be &quot;academic&quot; positions. They may or may not be &quot;senior&quot; positions. They may or may not involve advising/mentoring students, especially graduate students. They may or may not be open to tenure. A given institution might use either of the terms for something essentially the same as the other at a different institution.
If an institution uses both terms, you will have to ask them about the difference.
Of all the above only &quot;tenurable&quot; is unlikely, though a long term contract or an open ended contract is probably available. That would make it unlike a postdoc position.