>>38024
"They" works when, as posted above, you don't know someone's sex. It's usually used when referring to a person when the sex or name isn't given. "Singular they" actually does exist in a correct manner. It has to be paired with "someone/everyone/etc."
"When I tell someone a joke, they laugh."
"Hey, someone left their lunch right here."
In both of these cases, "they and them" refer to a single person.
"Everyone usually brings their bag with them."
This case is still using the singular they referring to one person. Every-ONE brings their bag.
Those were all nameless cases where it could apply to anyone. Once you get to names, it gets really awkward to read and write it.
"Frisk is a really nice kid. They helped us by breaking the barrier."
Who the fuck is they? In this example, "They" would refer to an unspecified group that broke the barrier, and not Frisk because Frisk isn't a group. It would be correct to use "He broke the barrier" or "She broke the barrier."
One last thing, in the English language, the generic "He" got into use. This is not the patriarchy at work – it's just simplicity. If you don't know someone's sex, you can use "he," and you will be in the clear.
tl;dr
The singular "they" without the proper grammar makes you sound like a tumblr idiot who doesn't understand English.