How do I know the difference between Definite and Indefinite Articles in Spanish

So, basically, a Definite Article in spanish, is something you know, for example, "El chico" is "The boy", he is someone you know, and a Indefinite Article is something or someone you don't know, for example "Un Bolígrafo" is "A pen", it's not The Pen. Please, if you don't understand it let me know it. Thanks :).

Explanation:

So, basically, a Definite Article in spanish, is something you know, for example, "El chico" is "The boy", he is someone you know, and a Indefinite Article is something or someone you don't know, for example "Un Bolígrafo" is "A pen", it's not The Pen. Please, if you don't understand it let me know it. Thanks :).

toilet paper: papel higienico

polar bear: oso polar

elephant: elefante

the only thing that makes sense that you couldn't find in a porta-potty, that should be there, would be toilet paper.

hope this