itch.io

What is this game? Ive never heard if it. Is PC game, table top?  How does it work, play on the internet somehow? I apologize for asking dumb questions. I stumbled on this by accident doing research on the crush depth and other specs of the German Type VII U-boat and the Gato class US submarine. And I came across a link to this. I initially thought the link had to do with subs. But I'm curious what exactly type of game u guys have going here. Thanks and again sorry for dumb questions