Don't know the real difference, but if you want to use emojis then UTF8mb4 is the way to go -> "Database character encoding: Ensure that your database is using the utf8mb4 character set and the utf8mb4_unicode_ci collation. This character set supports storing emojis and other Unicode characters properly." Though you still use `<meta charset="UTF-8">` in the HTML and set the following if you're using PDO ->
$dsn = "mysql:host=localhost;dbname=your_database_name;charset=utf8mb4";
$pdo = new PDO($dsn, $username, $password);