File permissions are a crucial security feature that controls who can read, write, and execute files and folders on your web server. They are represented by a three-digit numeric code (like 644 or 755) or a symbolic notation (like rwxr-xr-x). Each digit corresponds to a different user group:

• Owner (User): The user who owns the file.
• Group: Users who belong to the file's group.
• Public (World): All other users on the system.

For each group, permissions are defined for three actions:
Read (r / 4): View or copy the file's contents.
Write (w / 2): Modify or delete the file.
Execute (x / 1): Run the file as a program or script, or enter a directory.

Common Permission Examples:
644 (rw-r--r--): Owner can read/write, others can only read. Ideal for most web pages (HTML, images).
755 (rwxr-xr-x): Owner can read/write/execute, others can read/execute. Required for scripts (PHP, CGI) and directories.
777 (rwxrwxrwx): DANGEROUS! Everyone has full access. Avoid this setting unless absolutely necessary for a specific, temporary task.

Setting incorrect permissions is a common cause of website errors like "Internal Server Error (500)" or "Forbidden (403)". You can modify permissions through your hosting control panel's File Manager or via an FTP client. Always use the least permissive setting that allows your website to function correctly to maintain optimal security.