Blockchains aren't all that difficult really. Imagine you're kneading dough, and at every fold you're inserting a raisin at some specific spot. After 500 kneads, you have a really unique piece of dough that is virtually impossible to recreate or fake.
In the actual application, the raisin is a money transaction (user A transferring money to user B), and the dough is something called a "hash", which is a computer science thing, but the important part, to stick with the analogy, is that it's very easy to fold your dough another fold, but it's virtually impossible to "unfold" once it's done.
So, you have this ever-marching progression of folds, each fold incorporating the entire history of raisins/money transactions.
The folding is called "Bitcoin mining", but so that it doesn't grow out of bounds, they make it increasingly hard to fold. Because as an incentive to fold, you actually get money in return. So, the interesting thing about it that the act of recording the transactions, i.e. the folding, also makes you money, thus keeping alive the whole thing.