What exactly is this called? Pih, Pie or hyperpigmentation? How to fix it?

I rarely get acne or pimples, maybe 1 or 2 in a month. But I got a lot last year and the spots left behind from them have not faded, I have used tranexamic acid from minimalist and it has not worked In fading them, its not as noticeable in the pictures but in real life it's the only thing you can see. Can you guys educate me on what this is actually called and what will fix it, I've heard a lot of terms and I would really love if someone can explain it to me, thank you.