Does a PIP really guarantee that you’re getting fired?

I got PIPd today and I’m quite worried based off the comments and post I’ve read on here about PIPs. I like the place I work at so I’d prefer to make it work if possible. I’m just curious why a PIP guarantees that you’re getting fired. Is it not in your employers best interest to keep you if you’re able to actually improve and meet the objected they’ve layed out. Should I not try to improve to make it through.