Why is there so many daemons in Ubuntu?

[sandric]

Hi, I must be not understanding something, but I really cant understand, why in my output of ps -e so many '?' in terminal column.
I can understand the apache to be running in background as daemon, but even 'firefox-bin' or 'gimp'.

May be I dont understand the what is linux daemon? I always thought that this is processes with no terminal and they are the 'session leaders' of some process group. But When I run ps -d, trying to output all, except session leaders, I retrieve all with '?' in tty column.

I thought that all graphical programs must be run as 'tty7' processes, couse the Xorg is runned in it.

So, where am I got wrong, people?

[Rubberman]

A lot of those daemons are for hardware event handling such as handling hot-plug hardware or disc I/O. They are an integral part of the operating system for the most part, but some daemons are part of the desktop gui stack or other services that you have enabled, such as NFS or Samba file sharing.

[sandric]

but gui applications, such as 'mozilla' or 'gimp' are really deamons, or they just somehow attached to tty7, where is Xorg runned, it just to be consolidated with window manager?

[Siddly]

but gui applications, such as 'mozilla' or 'gimp' are really deamons, or they just somehow attached to tty7, where is Xorg runned, it just to be consolidated with window manager?

Xorg is the what your GUI - KDE, Gnome, Unity etc. needs in order to present a desktop. If Xorg and a Window Manager are not running then none of your graphical apps such as firefox, gimp, etc. just will not work.
Xorg runs on vt7, Gnome/kde etc. run on Xorg and gimp, etc. run on Gnome/kde etc.

To get a good appreciation of what is a daemon, see Daemon (computing) - Wikipedia, the free encyclopedia
It even explains the equivalents in Widows and MacOSX.