Okay here goes:
The blockchain is a database, but rather than being stored on a server like this website, it is stored by the users, and there are clever techniques to ensure it can't be corrupted. So think of it as you are users of this website, a bit of it is stored on your computer or smartphone for others to use. The advantage of this is that you don't have to pay for servers, back ups etc and theoretically it is more secure, so a lot cheaper to run.
The first blockchain was a made up currency called BitCoin, but there are thousands of blockchains now. Some are just currencies others are more than that.
Ethereum & Polka/Dot allow you to build your own applications. For Example
Socios.com is built using Ethereum, it is an App for sports fans to vote on club issues. City are on it.
TRX is yet to be launched, but will allow you to spend any of these currencies where you see Mastercard/Visa signs.
There are games like Alice and Alien worlds being developed which are a bit like Minecraft and World of Warcraft.
NFTs are concepts at the moment, but will be some sort of proof of ownership like a trademark, copyright etc. which is independent of state ownership.
So blockchains are capable of replacing a lot of servers, cutting costs on anything we do online.
When people say NFTs and BitCoin are Pyramid schemes, to some extent they are right, because that's driving the investment. However, there is real value in this technology in the next 5-10 years.
So it's the next generation of the Internet, that thing you all couldn't see the point of 25 years ago, which was never thing to catch on, e-commerce/Amazon was load of tripe, we'll never do that etc etc.
You'll have heard of mining, lots of people are paid a fraction of a BitCoin to run some complicated calculations to verify any changes to the block. This is called PoW and uses a lot of electricity. PoS is an alternative where the calculations are much simpler ie use a lot less electricity, but you need to deposit a lot of money to be trusted to do these (Ethereum is circa £30k-60k, but it varies a lot), which you will forfeit if you cheat. All blockchains are likely to move to PoS or die out.
I think that covers everything.