This is a specific HTML element found at the top of most index pages. In a file directory, the "Parent Directory" is represented by two dots ( .. ). Clicking this takes you one level up in the folder hierarchy.
This article dissects each component of this search term, explains how open directory listings work, and explores the ecosystem of "repack" media. index of 1080p parent directory series repack
This is a navigational term found on almost every open server. By including it in quotes, you filter out blog posts about movies and instead find the actual file repositories. This is a specific HTML element found at
: Use strings like intitle:"index of" "1080p" series repack or intitle:"index of" "parent directory" series 1080p to filter for server file listings. explains how open directory listings work