Operating System Detection: Nmap can discover the types of operating systems running on discovered devices in a process called OS fingerprinting.

Version detection — identifying applications and their versions; OS detection — determining the operating system along with ... to better understand what these systems are. $ nmap 192.168.0 ...

The -O switch tells Nmap you wish to perform an operating system fingerprint on the target. In order to do that, Nmap needs to be ran with root privileges in order to craft the raw packets needed ...