For your confusion, here's an article which comes from Telegraph that explained very well the "coinbase transaction" it's a different term on Coinbase exchange that has a domain name of "coinbase.com" if you're confused.

I tend to agree with the above said, that's how miners work through their proof of work algorithm and that's not generated from the air.
There are too many terminologies in crypto that you might confuse about if you aren't familiar with them.