first part of line in terminal

[Doug]

Before the ~$ on the terminal, there is--depending on how I installed 
the os, I guess--a two word
opening--I don't know what to call it.  On this particular distro, it 
says doug at dougpclos:  On another
machine, where I open up an Ubuntu terminal, it says doug at doug-MM061:

I assume that the first word--doug--is the user, i.e., me.  What is the 
second?  Is it a machine name?
I have to change it in various distros so as to make it consistent 
across several distros installed on any one machine.  So where can I 
find it to change it?  And what is MM0-61?  I'm sure I never put that in
myself.  (Another distro on that same machine does not have MM061; it 
has [doug at localhost ~]$  I don't
know why that distro has the [] either.)

I have looked at the various textbooks I have, but since I don't know 
what to call this, I haven't been able
to find it anywhere.

Hoping to learn--doug

PS:  I wish we could go back to the practice of slashing zeros, at least 
on screen.