Qual è la differenza tra aquella e ese/eso e for example, do both words mean “that”? how would you know when to use which word? ?Sentiti libero di rispondere con un esempio.

aquello/a and aquellos/as is for distant things both physical and temporal or for vague matters that are known in advance by the participants of the conversation.

¿Te acuerdas de aquello? —> Do you remember that [thing]?

¿Ves a aquel hombre de allí? Es mi papá —> Do you see that man over there? He's my dad

They're less used than "eso, esa, ese, esos, esas, esto, esta, estos, estás". I'll put the difference between these below:

First of all, in Spanish, nouns have masculine-feminine genders and singular-plural forms, for example:

el árbol, los árboles —> the tree, the trees (masculine in Spanish)

la casa, las casas —> the house, the houses (feminine in Spanish)

Having said that:

eso —> that (demonstrative pronoun for an indefinite noun, it has no gender since it's neutral) ex: eso me entristece (that makes me sad) replaceable with "it" (it makes me sad)

ese —> that (demonstrative adjective for a masculine definite noun) ex: ese perro (that dog)

esa —> that (demonstrative adjective for a feminine definite noun) ex: esa casa (that house)

esos —> those (for both indefinite nouns, in which case it works as a demonstrative pronoun with no gender since it's neutral, and as a demonstrative adjective for definite masculine nouns) ex: Dame esos (Give me those) replaceable with "them" (Give them to me). Esos niños (those children/boys)

esas —> those (demonstrative adjective for definite feminine nouns) ex: esas niñas (those girls)

esto —> this (demonstrative pronoun for an indefinite noun, it has no gender since it's neutral) ex: esto no me gusta (I don't like this) replaceable with "it" (I don't like it)

este —> (demonstrative adjective for a masculine definite noun) ex: este lápiz (this pencil)

esta —> (demonstrative adjective for a feminine definite noun) ex: esta camisa (this shirt)

estos —> these (for both indefinite nouns, in which case it works as a demonstrative pronoun with no gender since it's neutral, and as a demonstrative adjective for definite nouns) ex: ¿Qué son estos? (What are these?) replaceable with "they" (What are they?). Estos son mis aretes (These are my earrings). Estos hombres (these men)

estas —> these (demonstrative adjective for definite feminine nouns) ex: estas escaleras (these stairs). Estas mujeres (these women)