Blockchains are "public immutable ledgers"... If you understand those words, you can stop reading. Let me break it down.
Anyone can use it and no one controls it. If you do something on a blockchain, everyone in the whole wide world can see it. Don't do anything you wouldn't want your mom, your boss, or hackers on the other side of the globe to know about.
You can't take it back. Once you do something on a blockchain, it's done. It's impossible to change or delete what you did. REALLY don't do that thing you were thinking of before.
A database. Simple enough, yeah?
So, what's the big deal?
Databases have always been kept private and controlled by their owners. You had to go through the owner to do anything. That's because all previous databases were mutable. Making it immutable opened up the possibility of letting it be public.
Turns out a database with these properties opens up a whole host of possibilities.
Bitcoin is possible because no one can go in and give themselves free money, and no one can take away your money. They have to steal your "identity" (private key) to steal your money.
The same is possible for social networks on blockchain. No pretending to be someone else. No censorship. No company taking your data and selling it to the highest bidder.
Once you've solved the "money" and "social" apps with blockchain, pretty much everything else is an extension of that. Every app, website, and real life interaction is really just a spin on the money/social combination.
P.S. Disagree? Hit reply and name something you do that's not just a spin on money/social. Always happy to be proven wrong.