One of the things I find most interesting about Portuguese is the two versions of “that” it uses. It’s interesting for a couple reasons. First, because it indicates a different way of thinking about locations, and second, because of how it’s carried over into other areas, beyond demonstrative pronouns.
First let me explain the two versions of “that” and how they’re used. I’ll stick to the masculine versions to keep things simple, just know that feminine versions exist.
Of course, in English we have this and that, and this is used for something you have in your hand, or at least nearby (this mug [in my hand], this car [we’re in]), while that is used for things further away and/or nearer the person we’re talking to (that mountain [on the horizon], that wombat [gnawing on your leg]).
Portuguese speakers differentiate between “that wombat [gnawing on your leg]” and “that mountain [on the horizon]”. For things near the person being addressed they use esse, while for things distant from you and the person you’re talking to aquele is used. It’s interesting to note that the word for this este, which is very similar to esse (nearby-the-person-you-are-addressing that). For physical locations, it’s easy to know which to use, but when referring to more abstract things it can be tough to know.
This “near/far” distinction carries over into concept of there-ness. For a there next to the person you’re speaking to, aí is used, while lá is used to indicate a place neither of you is particularly near to.
The only parallel I can think of in English is when we add “over” to “there” (or “over there” to “that”). If you tell an English speaker, “It’s over there”, she is not going to look for ‘it’ near you or herself.
Naturally the border between “aí” and “lá is not a sharp one, and worse still, another word for “there” exists. “Ali” is used for a there that’s still near the person you’re speaking to, but not necessarily at hand. As an example:
“The pillow is there (aí – at home where you are), there (ali, near you) on the couch.”
“The bleach is there (aí – at home where you are), there (lá, away from you) in the laundry room.”
Not great sentences, but in informal or colloquial speech you will hear this sort of thing often enough.