¿Varón o hembra?

I remember the first time I heard the word varón like it was yesterday. 

This was a few year back and I was on an airplane speaking with a woman from Cuba and she used this word.  I was convinced it was some form of Cuban slang because I had never heard it before.  Turns out it wasn't, but I didn't think much about it until I heard it again much later.

Enough chit-chat, let me ir al grano (get to the point).

Varón and hembra officially mean male and female.   However, colloquially these terms are used to mean niño or niña, boy or girl, son or daughter.  Let's look at a few examples:

Tengo una nena y un varón
I have one girl and a boy

Tengo 3 hijos adultos 1 varon y 2 mujeres
I have 3 grown children, 1 son and 2 daughters

¿Vas a tener un varón o hembra?
Are you going to have a boy or girl?

Tengo un varón y una hembra
I have one boy and one girl

When you talk to someone who just recently had a baby and you ask them the sex of the baby, you might hear:

es un varoncito or es una hembra

These terms are also what you use for talking about male or female animals.  And you may also hear the word macho instead of varón.

¿Como diferenciar un gato macho a un gato hembra?‎
How do I tell the difference between a male and female cat?

That's it.  Getting a good handle on how these words are used will have you sounding like a born Spanish speaker.

Ojála que te sirva
I hope this helps!