Is it dead skin cells that come off when using an exfoliator?

I tend to use exfoliants a lot, especially during seasons like this when skin becomes rough. I am asking this question because I am curious about what exactly that dead skin-like substance is that comes off as soon as I apply the exfoliant to my face. How is it possible for something like dead skin to come off immediately after applying an exfoliant?

At first, I was really worried about using the exfoliator because I wondered if it contained some substance that caused it to react and slough off as soon as it touched my skin. Why? Could dead skin cells, like dirt, slough off immediately after application? Even if it is dirt, I find it suspicious that it sloughs off so quickly.

Because I had these doubts, I ended up not using exfoliants.

To ask one more time, is what comes off immediately after using an exfoliator dirt or dead skin cells?

Or could it be that the product itself contains a substance that causes a reaction?

I've been curious about this since I was young, but now that I'm older, I'm finally asking.