How to use iptables on Ubuntu?

I am looking the output of sudo iptables -L --line-numbers I got Chain ufw-before-forward (1 references) num target prot opt source destination 1 ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED 2 ACCEPT icmp -- anywhere anywhere icmp destination-unreachable 3 ACCEPT icmp -- anywhere anywhere icmp time-exceeded 4 ACCEPT icmp -- anywhere anywhere icmp parameter-problem 5 ACCEPT icmp -- anywhere anywhere icmp echo-request 6 ufw-user-forward all -- anywhere anywhere Chain ufw-before-input (1 references) num target prot opt source destination 1 ACCEPT all -- anywhere anywhere 2 ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED 3 ufw-logging-deny all -- anywhere anywhere ctstate INVALID 4 DROP all -- anywhere anywhere ctstate INVALID 5 ACCEPT icmp -- anywhere anywhere icmp destination-unreachable 6 ACCEPT icmp -- anywhere anywhere icmp time-exceeded 7 ACCEPT icmp -- anywhere anywhere icmp parameter-problem 8 ACCEPT icmp -- anywhere anywhere icmp echo-request 9 ACCEPT udp -- anywhere anywhere udp spt:bootps dpt:bootpc 10 ufw-not-local all -- anywhere anywhere 11 ACCEPT udp -- anywhere mdns.mcast.net udp dpt:mdns 12 ACCEPT udp -- anywhere 239.255.255.250 udp dpt:1900 13 ufw-user-input all -- anywhere anywhere Ufw sudo ufw status numbered [sudo] password for centa: Status: active To Action From -- ------ ---- [ 1] Anywhere DENY IN 192.168.0.13 This is just part of the output,but I can not decipher it. Ok I understand the protocol but anywhere means that everything is open? Where to read more?