It's a good but complicated explanation, I was hoping more for a layman's explanation. I guess what I really I want to know is what and how do I upgrade? Upgrade my wallet?
Sorry, when you said "What
exactly is a hard fork?" We thought you were looking for a technical explanation.
In layman's terms:
A hard fork is when different versions of software accept different transaction histories as being the "correct" "official" transaction history. At best, it results in transactions not being compatible between the versions of software. At worst, it creates a disaster where nobody can be certain any longer whether the transactions that they believe they've received or sent are recognized by the rest of the system.
As for "What" you upgrade, that would be your wallet software if you are running a full node or a SPV wallet. If you are using a hosted wallet (such as Coinbase, blockchain.info, BitStamp, localbitcoins, etc.) then all you can do is hope that they handle the situation appropriately.
As for "How" you upgrade, that would depend on what wallet software you are using. Generally it involves downloading and installing the most recently released version of the wallet software.