سلام دوستان.
من یه آفری اومده برام البته تازه ایمیل زدن:

Pending this review, we would like to offer you a graduate teaching assistant financial assistantship package for Academic Year 2016-2017 (spanning the Fall 2016 and
Spring 2017 semesters). This package includes a stipend of $20,000, a full tuition waiver, and optional healthcare coverage.

این کلمه optional منظورش چی هست؟ بیمه های همه دانشگاهها یک شکل هستند؟
ممنون