Neopronouns
Pronouns beyond he, she and they.
Neopronouns are third-person pronouns built outside the inherited set. The most established are ze/hir and xe/xem; others include ey/em, fae/faer and per/pers.
They aren't new in the way the name suggests. English speakers have been proposing alternatives since at least the 1850s, when thon was coined and briefly made it into dictionaries.
People use them for different reasons: because they/them still feels plural, because no existing option fits, or because the gap between existing words and their experience is simply too wide.
Using them takes practice and no more than that. Ask which set someone uses, use it, correct yourself briefly if you slip, and move on.