How exactly does mapping port 80 to port 80 work using the Digital Ocean Docker image?

I'm ruing Docker on DigitalOcean with the following commands:

docker build -t gs .
docker run -d -p 80:80 gs

I see it is ruing:

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                NAMES
a150619e2f3b        gs                  "/usr/bin/supervisord"   2 days ago          Up 2 days           0.0.0.0:80->80/tcp   nostalgic_swanson

I'm curious how port 80 maps to port 80 using the docker image on DigitalOcean. My Docker container is ruing Nginx:

root@docker-jz:/etc# curl -s -D - localhost -o /dev/null
HTTP/1.1 200 OK
Server: nginx/1.4.6 (Ubuntu)
Date: Wed, 24 Feb 2016 05:16:16 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 18278
Coection: keep-alive
Set-Cookie: session=eyJjc3JmX3Rva2VuIjoiM2RkMzRlYmEzMDkyZWFlN2Q5MGU0ZTY5ODhmOWFkY2JjZjRjNzMxZSJ9.Ca7OIA.LNpowRvpXV12byBTBmmMsN0ZUrk; HttpOnly; Path=/

But this is not what I expected. I expected to see an nginx or Apache2 ruing on localhost mapped to the docker container's Nginx. When I look at the contents of the server I see no apache or nginx:

root@docker-jz:/etc# ls
acpi                           dbus-1          init             ltrace.conf              protocols        skel
adduser.conf                   debconf.conf    init.d           magic                    python           ssh
alteatives                   debian_version  initramfs-tools  magic.mime               python2.7        ssl
apm                            default         inputrc          mailcap                  python3          subgid
apparmor                       deluser.conf    insserv          mailcap.order            python3.4        subuid
apparmor.d                     depmod.d        insserv.conf     manpath.config           rc0.d            sudoers
apport                         dhcp            insserv.conf.d   mime.types               rc1.d            sudoers.d
apt                            digitalocean    iproute2         mke2fs.conf              rc2.d            sysctl.conf
at.deny                        docker          iscsi            modprobe.d               rc3.d            sysctl.d
bash.bashrc                    dpkg            issue            modules                  rc4.d            systemd
bash_completion                environment     issue.net        motd.tail                rc5.d            terminfo
bash_completion.d              fonts           kbd              mtab                     rc6.d            timezone
bindresvport.blacklist         fstab           keel           nanorc                   rc.digitalocean  ucf.conf
blkid.conf                     fstab.d         keel-img.conf  network                  rc.local         udev
blkid.tab                      fuse.conf       landscape        networks                 rcS.d            ufw
byobu                          gai.conf        ldap             newt                     resolvconf       updatedb.conf
ca-certificates                groff           ld.so.cache      nsswitch.conf            resolv.conf      update-manager
ca-certificates.conf           group           ld.so.conf       opt                      rmt              update-motd.d
ca-certificates.conf.dpkg-old  group-          ld.so.conf.d     os-release               rpc              update-notifier
calendar                       grub.d          legal            pam.conf                 rsyslog.conf     upstart-xsessions
chatscripts                    gshadow         libaudit.conf    pam.d                    rsyslog.d        vim
cloud                          gshadow-        libnl-3          passwd                   screenrc         vtrgb
console-setup                  hdparm.conf     locale.alias     perl                     securetty        w3m
cron.d                         host.conf       localtime        pm                       security         wgetrc
cron.daily                     hostname        logcheck         polkit-1                 selinux          wpa_supplicant
cron.hourly                    hosts           login.defs       popularity-contest.conf  services         X11
cron.monthly                   hosts.allow     logrotate.conf   ppp                      sgml             xml
crontab                        hosts.deny      logrotate.d      profile                  shadow           zsh_command_not_found
cron.weekly                    ifplugd         lsb-release      profile.d                shells

If this is the case, when I hit the IP address of my server, how does it route to port 80 if neither nginx nor apache is installed?

- - , .