数据库连接中,DSN指什么?

数据库连接中,DSN指什么?
use Win32::ODBC;

my $DSN = "DSN = My DSN ; UID = sa; PWD = password";
my $data = new Win32::ODBC($DSN);
$data -> TableList;

在以上数据库连接程序中,DSN指什么?