What's the deal with le/les?

What's the deal with le/les?
 

What is the difference between:

Ella vende un cuaderno al hombre.

Ella le vende un cuaderno al hombre.

?

le is the indirect object, referring to hombre. Really, they aren't different

The second one is a construction in Spanish where the indirect object pronoun is used early in the sentence to determine the indirect object noun.

This pronoun is not always required, but it's more commonly used in everyday language and sounds better.

In short, both sentences mean the same but the second one is better.

;)

What's more, if you were referring to "the man" previously in your conversation, you can eliminate the reference to "the man"

Ella vió al hombre y le vende un cuaderno.

It is already understood that it was sold to the man.

At least for me the second ones is more correct for the translation into of the English

I hope your commentaries.