There is a comment attributed (almost certainly incorrectly) to Albert Einstein, in which the great physicist was asked to explain how radio works:
You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat.
Bitcoin and the blockchain can be explained similarly.
To understand Bitcoin, first you need to understand traditional “fiat” currency issued by governments.
Imagine a kind of huge spider spinning a web. The spider creates an intricate network of connections that form a complex, interconnected structure. The spider keeps slowly adding new links to make the web bigger. If a part of the web breaks, or an anchor pulls loose, the spider fixes it. When the spider is done, you can move from any point on the web to any other point. Pull on it anywhere, and even though it is made up of gossamer threads, it has a surprising strength and resiliency. Something that gets stuck in the web will very likely stay there.
That’s how fiat currency works. Do you understand this?
The blockchain technology supporting Bitcoin operates exactly the same way. There is a resilient, interconnected web, and things placed there will stay put.
The only difference is that there is no spider.