Traditional wingers hug the touchline to cross with their natural foot. An inverted winger does the opposite: a right-footer on the left, a left-footer on the right.
This forward angle creates natural cutting runs inside the box, combinations with the 10 and overloads in the half-space. It also frees the full-back to overlap and provide the width.
The concept has gone from niche to mainstream: Robben, Salah, Son and countless others built careers on cutting inside.