Both videos do a pretty good job at explaining it better than I could, but if don't have time for a video, the lowdown way I'd explain it is firstly, even though it has a 2 in the title you don't need to have played the first game to experience it. It's a bit different, but just like how you don't need SH1 to play SH1, you don't need to have played Pathologic 1 to play Pathologic 2.
Anyways, Pathologic 2 is sorta' the antithesis to the current game design trend we see, it has masterful writing, music, atmosphere, art design, but moreso everything peddles so well into each other to deliver a very unconventional game experience. An example I can give is we as gamers are so used to video games holding our hand to do what it wants us to do. We receive a quest, we do it, we get rewarded, etc. But what if there was a game where the game was lying to you, and there was a far deeper reason it was. Where story quests aren't needed to progress the game, the story goes on with or without you because the world doesn't revolve around you. That mindlessly doing what others tell you is not the way to succeed in the world, you need to pay attention to information everyone is telling you because some people either are lying to you for their own benefit (and not in a big "plot twist way", little lies you may or may never pick up) or some are just wrong about what they believe, and doing what they want will actually make matters worse?
There's a lot more to it, but Pathologic is a game taking place over 14 days where a plague is hitting a small Russian town that's full of weird surrealism and beliefs, you're a doctor who went to university to study medicine but go back to your hometown to find out your dad's been murdered alongside someone else and big parts of the town suspect you did it for reasons you need to discover. And I'm trying my best not to spoil it, but everything in the game ties to its themes. Dying in the game and game overs actually play into the story, you're constantly struggling to survive and have to make really tough choices, sometimes with limited information at that point in time due to your previous choices. and not on a stereotypical "Good or Bad" scale, it becomes a plight for survival. BUT, what holds the game together to make the misery worth going through is it's an incredibly well written and realized experience that does have a point, and while most games focus on "Empowerment" of the player, Pathologic 2 focuses very heavily on what can be interesting and worth an experience that constantly disempowers them and has you working against a world that really seems to want you dead.
There's a lot more to it than I'm saying and I'd recommend watching a bit of the videos, this game isn't a "fun" experience traditionally, but it's really compelling and I think is a game that's going to be remembered down the line. It's really unique, interesting, and I'd even say well-done that is doing a lot with all of its elements...