Momma Vs Mom: No, It's Not The Same Person

I've mentioned Mom (aka Mommy #2 sometimes) before but I have never really explained how things work.  Mostly because no one has ever asked and it's too complicated for me to try to explain without any prompting.  However, it has been brought to my attention that people may be confused so here it is: Who is Mom, who is Momma, and how the heck does a child get this?