What is the name of the program that displays the notifications?

What is the name of the program that displays the notifications in ubuntu ? The ones like sound changes, song name (in rhythmbox) etc. Can I send my own custom messages to it ?

quick answer

notify-send "Message Title" "The message body is shown here" -i /home/andrei/Pictures/image.png -t 5000

The program is called notify-osd, you can use the tool notify-send to send messages to it from scripts and your programs and so on:

• How do I send text messages to the notification bubbles?
• Where can I find documentation for notify-osd?

Caveat!

    notify-send "Message Title" "The message body is shown here" \
             -i /home/andrei/Pictures/image.png -t 5000

is desktop conditioned, depending on whether it is:

1. Unity's notify-OSD or
2. Gnome's notification-daemon

that displays the notification.

Quoting mhall119/devportal/notify-osd - Ubuntu Wiki:

notify-osd

... takes the place of notification-daemon, and its presentation of notification bubbles differs in several ways ...

In the ubuntu 12.04, Unity (version?) desktop environment, quoting manpage man notify-send

NAME
       notify-send - a program to send desktop notifications   
   ...
OPTIONS
   ...  
       -t, --expire-time=TIME
              Specifies  the  timeout  in  milliseconds at which to expire the
              notification.

however, contradicting it's use by notify-OSD,
quoting from Notification | Ubuntu App Developer(developer.ubuntu.com/resources/technologies/notification/), specifically section Non-expiring_notifications:

  ...every bubble closes by itself after a timeout. This timeout is based on the
  length of the bubble’s text; Notify OSD does not use the expire_timeout parameter ...

The -t 5000 may or may not behave as expected.

ref:
Where can I find documentation for notify-osd?

Bookmark:
What is the name of the program that displays the notifications?