What's the weird route stuff?

Hi! I just started playing deltarune a few days ago because I wanted to wait till there is a bit of content so I don't have to wait a lot to play one chapter. And naturally I haven't been in the fandom much.

So my question is what is all this weird route stuff? I thought the point of the game was "your choices don't matter" so I thought there weren't going to be multiple routes.

If you could try to keep this spoiler free would be great but if it's needed to get what it is then go ahead. Thanks!