chflags is a command line tool in Unix-based operating systems, including macOS and FreeBSD. It stands for "change flags" and is used to modify file or directory flags. Flags are special attributes that can be set on files or directories, providing different functionalities and behaviors. Each flag has a unique significance, and chflags allows users to set, unset, or change these flags as needed. The tool requires administrative privileges to modify certain flags. Some common flags that can be modified using chflags include the hidden flag to hide files or directories from the graphical interface, the immutable flag to make files or directories unchangeable, and the restricted flag to prevent modifications by anyone other than the owner or the superuser. chflags provides users with granular control over file and directory attributes, making it a powerful tool in managing and securing files in the command line interface.