When you're learning a new language, you start with, "hello world".
It's tradition, just a thing that you do - though most of us don't actually knuckle down and type it in. Instead, we skim that chapter and get on to the good stuff.
I have my own "hello world" program that I like to write in every new language I learn. It's simple enough to be simple and hard enough to mean I have to read a couple more chapters than I probably expected. Because it's personal to me, I can't cheat by writing something more along the lines of the tutorials I find online. Because it's the same thing every time, it means that if I only manage to sort-of finish it, I obviously haven't learned enough and I feel sad.
I encourage everyone to do this. You feel you're getting somewhere with the new language rather than wallowing in theory, and you find out that what took 50 lines in your favourite language up until now takes 10 in this new hipster script you're looking at. Maybe it's worth investing more time?
Mine's something that takes a word and works out how to write it using only the symbols available in the periodic table. It usually means a list type and some recursion.
You can choose your own. If you do, let me know :)