Since "[S6E1] Chapter 1" is not a standard official title for a single major TV episode, it most likely refers to the of a series that uses "Chapters" as its naming convention (like American Horror Story or The Mandalorian ) or a specific fan-fiction project.
From teeth raining from the sky to mysterious videos found in the basement, the episode masters the "slow burn." [S6E1] Chapter 1
Game of Thrones S6E1: “The Red Woman” | Off The Bookshelf Since "[S6E1] Chapter 1" is not a standard
The episode introduces us to Shelby and Matt Miller as they flee a traumatic incident in Los Angeles for a seemingly peaceful farmhouse in North Carolina. Like many classic horror setups, the "peace" is short-lived: [S6E1] Chapter 1
While not titled "Chapter 1," it is the Season 6 opener that famously confirmed Jon Snow's fate (initially) and revealed Melisandre's true form.