There are a few things you could do to try and ascertain what's running on your system. While it's not guaranteed, it is very likely that any production services running will have been made available, either on the local subnet only or via NAT, to the network. With this in mind you can check what ports your server is listening on to get an idea of what's on there. A good command to use would be:
alex:~/ $ sudo netstat -tulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 945/smbd
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 1746/nginx
tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 1437/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1310/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 3746/cupsd
As you can see from the example output above, it presents you with the protocol version (tcp or udp), the address that's being listened on, the port that's open and the program that's listening.
In the above truncated example (a desktop machine) you can see tcp ports 139, 80, 53, 22 and 631 are listening. These resolve to samba, http, dns, ssh and ipp respectively, and is confirmed when you check the program that's listening on that port.
Additionally, most Debian and Red Hat based Linux Distributions use system V and have the services command available. You can use this to provide a list of services and their states:
alex:~/ $ sudo service --status-all
[ + ] acpid
[ - ] anacron
[ + ] apparmor
[ ? ] apport
[ ? ] atieventsd
[ + ] avahi-daemon
[ ? ] binfmt-support
[ + ] bluetooth
[ - ] brltty
[ ? ] console-setup
[ + ] cron
[ ? ] cryptdisks
[ ? ] cryptdisks-early
[ + ] cups
[ + ] cups-browsed
[ - ] dbus
[ ? ] dns-clean
[ + ] dnsmasq
[ + ] ebtables
[ + ] friendly-recovery
[ - ] grub-common
[ ? ] irqbalance
[ + ] kerneloops
[ ? ] killprocs
[ ? ] kmod
[ + ] libvirt-bin
[ ? ] lightdm
[ ? ] networking
[ + ] nginx
[ + ] nmbd
[ ? ] ondemand
[ + ] openvpn
[ ? ] pppd-dns
[ - ] procps
[ - ] pulseaudio
[ ? ] rc.local
[ + ] resolvconf
[ - ] rsync
[ + ] rsyslog
[ + ] samba
[ - ] samba-ad-dc
[ + ] saned
[ ? ] sendsigs
[ - ] smartmontools
[ + ] smbd
[ ? ] speech-dispatcher
[ - ] ssh
[ - ] sudo
[ + ] udev
[ ? ] umountfs
[ ? ] umountnfs.sh
[ ? ] umountroot
[ - ] unattended-upgrades
[ - ] urandom
[ ? ] vboxautostart-service
[ + ] vboxballoonctrl-service
[ + ] vboxdrv
[ + ] vboxweb-service
[ + ] winbind
[ - ] x11-common
This gives you an overview of system v services - if you have custom applications that are started manually or have custom startup scripts they may not be here, but this is still useful. A + indicates a running service, a - indicates a stopped service and a ? means unknown. Be sure to run both of the above commands as an elevated user, otherwise your results will be incomplete.
The above commands will give you insight in to what's running on your server, but not how it's configured or it's purpose. An open port 80 indicates a web server, but that could mean public facing, internally presented API, httpd installed by accident, any such config. Ideally you need to discuss with the architects to get a better idea of each server's purpose.