Hello everyone. I am quite new to Bitcoin, yet I do understand the basics.
Welcome to the world of Bitcoin. This is an exciting place and there is potential to make a lot of money. Please be careful though there are a lot of scammers out there and if they get their hands on your coins there is no way to get them back. Be very wary when buying or selling coins and make sure you use an exchange or a trusted Escrow service. There are a few on this forum as far as I know.
One of the questions I would like to be clarified is how the Bitcoin 'coins' are capped off at 21 million? What stops a hacker from just randomly creating new coins?
The network is protected against this kind of behavior. It controls the flow of coins. As @pooya87 said, the network will just reject any new coins created by hackers. The only way they can do it successfully is by creating their own altcoin but that comes with its own set of problems and without trusted backing its not likely to gain any traction.