Final answer:
The subject of this question is CSS Selector. CSS selectors are used to target specific HTML elements and apply styles to them.
Step-by-step explanation:
The subject of this question is CSS Selector. CSS stands for Cascading Style Sheets, and it is a style sheet language used for describing the look and formatting of a document written in markup languages like HTML.
In the given question, the term '.onetrust-pc-dark-filter:not([class* a)' represents a CSS selector. CSS selectors are used to target specific HTML elements and apply styles to them. They allow developers to select elements based on their attributes, classes, or other characteristics.