a popular constructed-language. it is an international-auxiliary-language.
it was made by guy who wanted there to be an easy language so everyone can talk in it and be friends. :)
then ww1 broke out. then ww2 broke out. some people in power banned or pushed back against the language because they were evil or french.
it's somewhat popular in china. the chinese government offers their news in esperanto.
it's also popular in japan to a lesser degree. there's a series of japanese visual novels aimed to teaching esperanto. the esperanto vr chat world is run by the japanese esperanto community.
most of the vocabulary comes from european languages. the grammar is flexible; it has a simple conjugation system, mostly free word order, and is agglutinative.
there are active mastodon, discord, telegram, and matrix communities for speakers of the language.
it has a duolingo course.