See all open ports of a host
$ nmap thehost.com
See all the open ports with service versions
$ nmap -sV thehost.com
See more information with aggresive scan
$ nmap -A thehost.com
Some nmap script examples
$ nmap --script banner thehost.com
$ nmap --script http-headers thehost.com
$ nmap --script http-enum thehost.com
$ nmap --script dns-brute thehost.com