Suppose you are in a tenure-track position in the US and lucky (or successful) enough to eventually get tenured.
The most important effect is obvious that you now have a permanent position. But what other effects are there? Does your salary increase automatically? Does your teaching load change? Do you get (additional) grad students? Are these changes negotiable?
PS: I am outside of the US system but interested in these facts for the purpose of comparison.
Tenure and faculty rank are somewhat independent in that a faculty member may be hired as an associate (or even full) professor without immediate tenure- in those cases the faculty member is typically awarded tenure after a shorter than usual probationary period of a year or two.
The more common situation is when a faculty member is hired as an untenured assistant professor and then awarded tenure and simultaneously promoted to associate professor after a fairly long (up to seven years) probationary period. I'll focus on this common case in the US.
Does your salary increase automatically?
There is typically a pay raise given to faculty who are promoted, but this could be small (a couple of percents) or large (twenty percent) depending on the institution. There might be a standard pay raise, or it might be determined on an individual basis. At institutions with unionized faculty that pay raise would be part of the contract.
Does your teaching load change?
At some institutions, tenure-track assistant professors have a reduced teaching load which goes up when they're promoted. It would be very unusual for the teaching load to be reduced due to promotion and tenure.
Do you get (additional) grad students?
Graduate students in the US are typically supported by research assistantships (which are under the control of the faculty members who are PI's on the grants that fund the assistantships) and teaching assistantships (which are awarded to students by the department.) Students typically ask to work with an academic advisor and then either get an RA from the advisor or are supported by a departmental teaching assistantship if they can get one.
Thus promotion to associate professor doesn't really have any direct effect on your ability to support graduate students.
However, students may be more interested in working with you after you've been tenured. Students are rightly concerned about starting to work with an inexperienced assistant professor who might not get tenure and leave them with a half-finished thesis. Another issue is that in some disciplines (pure math is an example) it's traditional for assistant professors to focus more on their own research than supervising graduate students. In that situation, a newly tenured professor might be more willing to take on students.
Are these changes negotiable?
It's always possible for a faculty member to ask for a pay raise or a reduction in teaching load. However, you're unlikely to be able to negotiate a pay raise or different working conditions just because you've been recently tenured. The norm is that faculty members who are tenured will simply accept a pay raise and continue their work.
Does your salary increase automatically?
It depends. Tenure may or may not come alongside a promotion (but often does). The increase in pay that comes from that promotion may be small or large - there are some universities where the move from Assistant to Associate Professor with Tenure is a major bump in pay, and others where it's relatively modest to encourage people to go after Full Professor.
Does your teaching load change?
It...depends.
You may have more sway in what classes you teach, which may enable you to shift your teaching load toward classes you find more desirable.
Do you get (additional) grad students?
It's possible that your promotion might come with a funding line for a graduate student, but I've honestly never seen this. Your ability to support graduate students is largely a function of recruitment and funding. Indirectly you might have more sway on admissions committees to shape the incoming class in a way where it's easier to draw people into your lab, but that's a pretty indirect method.
Are these changes negotiable?
Getting tenure might make you more (or less) interesting as a recruitment prospect at another university. If you have another offer, everything is negotiable. But "I got tenure, now give me more things..." is not something that happens automatically.
