The state is either open, filtered, closed, or unfiltered. Open means that an application on the target machine is listening for connections/packets on that port. Filtered means that a firewall, filter, or other network obstacle is blocking the port so that Nmap cannot tell whether it is open or closed. Closed ports have no application listening on them, though they could open up at any time. Ports are classified as unfiltered when they are responsive to Nmap's probes, but Nmap cannot determine whether they are open or closed.
david@david-nb:~$ sudo netstat -tunlp
Aktívne internetové spojenia (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 5507/exim4
udp 0 0 0.0.0.0:35986 0.0.0.0:* 5238/avahi-daemon:
udp 0 0 0.0.0.0:68 0.0.0.0:* 6013/dhclient
udp 0 0 0.0.0.0:5353 0.0.0.0:* 5238/avahi-daemon: