h1 is the element. “Hello” is the text within the element. The goal of challenge was to simply change the text within the element from “Hello” to “Hello World”. You added another h1 element, which is incorrect.
I believe you are on the Basic HTML and HTML5 exercise, if so you can click run test and once it is passed, you can move to the next challenge.
However, it appears there is a little error. You are expected to write the Hello World in the same tag.