When an English speaker says 'The mom', they are talking about someone elses mom. When we say 'Mom', we are talking about our own mom. For example, I would never ask my brother where 'the mom' is when asking where our mom is.
If I was describing someone elses mom, I would begin the sentence with 'The mom'.
In this case in Russian we usually use pronouns for somebody's moms. Like "where is your/his/her mom?" And when I mean my mother I would say it without pronouns simply "где мама?" or "my mom" and "our mom" if I talk to my sister.
Only when we speak to kids we can say "mom" meaning his mother.