What are the computers actually doing when mining bitcoin?

So one complaint about bitcoin is all the energy used during mining. Bitcoin isn’t a physical thing — it doesn’t require work to generate it. If you want a million bitcoin, you just increase a variable. But that would just create inflation. The mining must provide something of value that the new bitcoin is being generated and exchanged for. So what is that computer generating? Is it something like folding@home, where the processing power is solving a problem (in that case, calculating protein folding) for someone who is then giving you new bitcoin for it? ChatGPT uses a lot of power, but it is providing an answer to a question. Whoever is generating the new bitcoin, what are they gaining from you mining it?