What on earth causes blackheads? I keep getting them and I'm worried.

Lately, I've been getting blackheads on my nose and chin, and I'm really worried about them. I'm not sure if they're caused by sebum or dead skin cells. I'm diligently washing my face, but it's not working.

They say you need to properly understand the causes of blackheads and manage them. But do eating habits have a big impact? Anyone who has experienced the causes of blackheads, please give me some practical advice on how to manage them!