An appositive is a noun or noun phrase that renames or clarifies another noun or noun phrase. In this case, "member" clarifies what kind of student council Stacey is a part of.
Here's how it works:
* The main noun: "Stacey"
* The appositive: "(member)"
* The appositive phrase: "(member) student council"
The phrase "(member) student council" gives us more information about Stacey's role. It tells us she's not just a student, but a student who is also a member of the council.
Even though the parentheses are used here, it's important to note that appositives are often set off by commas as well.