Qual o objetivo do código abaixo?

$dsn = 'pgsql:dbname=testdb;host=127.0.0.1';
$user = 'dbuser';
$password = 'dbpass';
try {
    $dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}
$count = $dbh->exec("update aluno set nome='Rodrigo' where matricula='201712345') ");
echo " $count registro(s) ";