Question

A element is a descriptive word phrase or clause that is not essential to the meaning of a sentence

Answer 1

Nonrestrictive I just took the quiz

Answer 2

Answer;
A nonrestrictive element or a nonessential element

Explanation; 
A word, phrase or a clause that is not essential to the meaning of a sentence is referred to as a nonessential element.
When this type of element is removed from a sentence,the sentence still makes sense since it is not essential.
For example;
In the sentence; The information, however, was inaccurate.
However is the non essential element since it interrupts the flow of the sentence, removing it the sentence would still make sense. that is; 
The information was inaccurate.