Demostrative pronouns
Neuter pronouns / Indefinite demonstrative pronouns
Neuter pronouns, also known as indefinite demonstrative pronouns, refer to unspecified or unknown nouns, object, situations, 
and ideas or concepts or are used when there is no specific reference to a noun. 
This neuter pronoun do not have accent because they have no corresponding adjective forms. 
esto Esto lo tenemos que hacer mejor. This we must do it better.
Eso es imposible. That is impossible.
¿Qué es esto? What is this [unknown object]?
Ésto es bueno. This [referring to a situation rather than a specific object] is good.
Esto se tiene que vender. This has to sell.
eso ¿Viste eso? Did you see that?
Compró su primer auto, por eso esta contenta. She bought her first car,  because of that she is happy.
Tienes que comprar pan. Recuerda eso. You have to buy bread. Remember that.
No quiero que vuelvas a decir eso I dont want you to say that again
Por eso, no puedo hacerlo. Therefore (because of that), I can't do it.
aquello Recuerda aquello que hablamos. Remember what we were talking about.
Todo aquello fue asombroso. All that was amazing.
Aquello no es necesario. That's not necessary.
They also are used in certain idiomatic phrases. 
Acuérdense de eso.  Remember that
Por esto.  For this reason
Es por eso.  That's why
Esto es lo mío I feel confortable with this ( a job, a hobby, a place) (unknown object, drink, etc)
¿Qué es esto?  What is this ?  (object, drink, event…)
Ésto es bueno.  This is good.
Todo aquello le pertenece. All that is yours
No olvide eso.  Don't forget that.

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