Find-file-up navigates up the directory tree, searching for a file with a specified name. Starting from the current working directory, it traverses upwards, checking each parent directory until the file is found or the root directory is reached. Useful for locating configuration files or project-related assets without needing to know their exact location within the file system. Returns the absolute path of the file or null if not found. Simplifies finding files common across a project, like .eslintrc.js or package.json.