Your safety might be my reach, or vice versa.
As said above, a safety is a school that you know you will be accepted to, you know you can afford, and you would be willing to attend. Hopefully “willing to attend” includes having a good program in the student’s intended major.
Schools that have highly predictable stats-oriented admissions can be a safety for some students, a reach for students that are very close to the cutoff, and out of reach for many other students.
Schools that are expensive might be a reach for some students even though they know that they will get in, because they do not know for sure whether they will be able to afford it. A different student with the same stats but a wealthier family might have the same school as a safety because they know they can afford it.
I doubt that Villanova is a safety even for most students who have some realistic chance to get accepted to an Ivy League university.
Admissions in the US is in many cases hard to predict, which can make it hard for some students to pick two good safeties to apply to.