* Colloquially, we use the term "professor" to refer to anyone who teaches at a university, but it's probably not her actual job title. For example, at my alma mater, non-tenure-track instructors typically have the title "Senior Lecturer", but everyone calls them professors.

* There is a difference between "tenure" and "tenure-track". It's possible to not have tenure but still be in line to receive it upon a future promotion. If your position isn't tenure-track, though, then you will never get tenure unless you leave your job and find a tenure-track position elsewhere. As there are few tenure-track positions open, this is harder than it looks.

* For actual professors (i.e. tenure-track jobs with "Professor" in the job title), the entry level position doesn't carry tenure, and it comes with a promotion. They start out as an Assistant Professor, get promoted to Associate Professor, and eventually to full Professor. Tenure is typically granted with the promotion to Associate Professor.