Interactive Mode (--interactive)
Nmap's interactive mode isn't mentioned in the nmap man page, but it is identified on the online quick reference screen (-h). The interactive mode is included with nmap to assist with managing an nmap session and to provide an easier method of spoofing the nmap session to be more invisible on a system.

The commands available in --interactive mode are similar, but not identical, to the commands available from the nmap command line. For example, the --spoof command in interactive mode is comparable to the quash argument vector (-q) command on the nmap command line.

This interactive mode can also be called automatically if the nmap binary is renamed to one of many different options. These name options are BitchX, Calendar, X, awk, bash, bash2, calendar, cat, csh, elm, emacs, ftp, fvwm, g++, gcc, gimp, httpd, irc, man, mutt, nc, ncftp, netscape, perl, pine, ping, sleep, slirp, ssh, sshd, startx, tcsh, telnet, telnetd, tia, top, vi, vim, xdvi, xemacs, xterm, and xv. As this list implies, renaming nmap to a less conspicuous name can increase security while simultaneously providing a simple method of starting nmap in interactive mode.

The online interactive help screen is shown below. As the examples at the bottom of the help screen show, the commands and functionality in interactive mode are similar to those on a normal nmap scan:
# ./nmap --interactive

Starting nmap V. 3.81 ( )
Welcome to Interactive Mode -- press h <enter> for help
nmap> h
Nmap Interactive Commands:
n <nmap args> -- executes an nmap scan using the arguments given and
waits for nmap to finish.  Results are printed to the
screen (of course you can still use file output commands).
! <command>   -- runs shell command given in the foreground
x             -- Exit Nmap
f [--spoof <fakeargs>] [--nmap_path <path>] <nmap args>
-- Executes nmap in the background (results are NOT
printed to the screen).  You should generally specify a
file for results (with -oX, -oG, or -oN).  If you specify
fakeargs with --spoof, Nmap will try to make those
appear in ps listings.  If you wish to execute a special
version of Nmap, specify --nmap_path.
n -h          -- Obtain help with Nmap syntax
h             -- Prints this help screen.
n -sS -O -v
f --spoof "/usr/local/bin/pico -z hello.c" -sS -oN e.log


Noninteractive Mode (--noninteractive)
Nmap's non-interactive mode doesn't currently provide any additional functionality, since the --noninteractive option is already the default operation. If future nmap functionality requires user input, this option could be used to force nmap into a non-interactive option that would be useful for unattended nmap scripting.