simple but usefull – you have the ip address of an computer in your local LAN – but you don’t know it’s computername.
for internet-usage the host command is usefull because it shows – if a website is reachable by IPv6 or not. (your LAN network needs to operate in IPv6 in order to ping6 host)
suse12:~ # host 172.20.0.7 126.96.36.199.in-addr.arpa domain name pointer COMPUTERNAME.DOMAIN.local. suse12:~ # host yahoo.de yahoo.de has address 188.8.131.52 yahoo.de has address 184.108.40.206 yahoo.de has address 220.127.116.11 yahoo.de has address 18.104.22.168 yahoo.de has address 22.214.171.124 yahoo.de mail is handled by 10 mx-eu.mail.am0.yahoodns.net. suse12:~ # host dwaves.de dwaves.de has address 126.96.36.199 dwaves.de has IPv6 address 2a01:4f8:c17:1b24:2:: dwaves.de mail is handled by 10 dwaves.de.