What do PHP errors: Warning, Notice, Fatal Error mean and how to fix them?

Hello everyone! I'm a beginner in PHP and constantly encounter various errors that are displayed on the screen or in the log. Most often I see "Warning: Undefined array key", "Notice: Undefined variable", and sometimes "Fatal error: Uncaught TypeError". I understand that this means something is wrong, but I can't figure out how they differ and how to properly fix them.\n\nFor example, I have this code:\n\n```php\n 'Ivan'];\necho $users['moderator'];\n\n$result = 10 / $unknownVar;\n?>\n```\n\nIt produces several errors at once: Notice about an unknown variable, Warning about a non-existent array key, and Warning about division by zero. I don't understand why the code continues to run but still displays these messages. In other languages