apologies first as English is not my first language.

I would really appreciate if anyone could explain the concept of hardfork.

As I understand it, if there is a hardfork with say, bitcoin, everyone who own X amount of

bitcoin gets X amount of hardforked coin as well.

For example, if bitcoin platinum were real, a person who owns 15 bitcoins would've got

15 bitcoin platinums.

But, software engineers who hardforked ended up with tons of them.

For example, litecoin developers ended up with tons of litecoin.

How did this happen? Also, how can I study about the blockchain technology?

And if one hardforks a coin, how do you acquire the mainnet (the network)?