What is Reusable abstraction of a system ?

What is Reusable abstraction of a system ?

Abstraction is a representation that captures only essential aspects of something, reducing the complexity apparent to the user. Reusable abstraction means general abstraction that can be reused.  Lets take example of LMS. Every VU student uses it. Course website is a reusable abstraction as courses are different in each degree but every student is using course website of its own subjects.