Esperanto is a constructed language, first designed by L.L. Zamenhof in 1887, intended to serve as an international auxiliary language. It features an extremely simple and regular grammar, with a vocabulary largely derived from combining word roots and affixes so learners would have less to memorise. It is the most widely-spoken conlang in the world, with an estimated one million people able to speak it to some degree.
I first came across Esperanto when I was in year 7, and was immediately attracted to its internationalist values. I liked the idea of a simple, neutral language that could serve as a universal second language. Unsurprisingly, Esperanto has historically been popular among many parts of the internationalist Left, especially in the first half of the twentieth century, with speakers facing repression under dictatorial regimes like Hitler’s or Stalin’s that wanted to drum up nationalist hatred among their own population against their neighbours’.
I still really like the idea of Esperanto, even though I think Esperanto itself has numerous flaws and that the “reformed Esperanto” Ido is much better. Esperanto having about three orders of magnitude more speakers, though, means it has more resources which makes it easier to learn. For example, I first studied Esperanto on the website Lernu! ; these days there is also a Duolingo course which is well-regarded.
Esperanto is sometimes referenced in pop culture, too. For example, early seasons of the TV show Red Dwarf included signage on the ship in Esperanto, and had the character Rimmer trying to learn it, in order to add to the ship’s depiction as an international operation.