Bitcoin was the very first solution to how do you prevent a digital item from being copied and used repeatedly aka double spending.

Nothing digital was truly safe from this until bitcoin as you always had to trust someone who could double spend or steal it if they wanted to, or the database/system being hacked and things altered.

Things became truly immutable once committed to the chain.

The whole system needed an incentive to keep everyone aligned to reject double spends, and the coin itself was the reward. (Edit and there's a limited number of coins, making them scarce)

Miners get rewarded for ensuring transactions are legitimate. It costs money to gain the reward so it's better for them to just keep the reward instead of risking losing it

Edit: it also created the first time we could prove something digital existed at a point in time. Everything before this involved trusting someone data wasn't altered to 'prove' it. Since blocks are immutable, their timestamp proves something existed then. E.g. a hash of a picture. It's irrefutable the picture existed on that day.

You know the blockchain, right? Basically, whenever anyone trades a bitcoin, that transaction is recorded on the blockchain. And there's a bunch of math work that goes into recording each transaction. When people do this math work, they get rewarded with a tiny bit of a bitcoin. This is what mining is. So then you have some bitcoin. And some other people accept bitcoin for goods and services.

Bitcoin itself is a virtual currency, just like Runescape gold or the dollars in your online bank account. It's just numbers on a computer. The blockchain part is what makes it different.

Now don't get me wrong, for the majority of applications this is overkill and not at all useful. Bitcoin and blockchains are solutions looking for a problem.

A confidence game too many people believe in

A way to milk money from people who don't understand how computers work.

"Money" that's only used to buy drugs or try to get rich quick.