![](https://steemitimages.com/DQmTrusFJtHP2vuXnnGLkXhEmCTUuPMZWGG13MMLVe69tsQ/image.png)

The work test is the key to the whole blockchain ecosystem, to the accounting book where the movements are recorded, we are going to stop calling it a book and we are going to call it a block chain.

The book has many pages where we will write down the transactions, to each of those pages we call it a block, each page has a size limit, if we speak of a DIN A5 notebook for example, we can still fit 20 transactions on a page, but if we make the notebook a little bit bigger and we take it to an A4 example; a paper, a sheet, then more transactions will come right?

Blockchain works in the same way, we do not speak of an accounting book but of a chain of blocks and to each of these pages we call it a block.
It is called a chain of blocks because each page is referring to the previous one, they are all linked, and why do we do this? It turns out that to generate a page in this book, it is necessary to follow transactions that are generated, not by us, but by many users of the network, it is necessary to perform a work test.

It is a mathematical algorithm resolution, a test that is complex to solve and that can also be adjusted in difficulty.

### What do we get with this?


![](https://steemitimages.com/DQmeHprZpT4GDHiTJzZfCdRRfZC2tvSr7DZVwbyfFbzMGMo/image.png)

If they generate a waste of time, this means that they will modify the pages of each home, modify the page of the book, modify all the pages that are ahead of the two. 

Imagine if it is the complex that generates one of the cities, how complex all the stages that followed were generated, if I want to change a transaction that was made a while ago, so that the Tetris time was valid.

Why when one of these chips falls and chips are falling on top, it is more difficult to separate the chip, it is more difficult to modify it. In the same way in the chain of blocks, when a transaction is inserted in the chain of blocks, in one of the pages, and more blocks are generated above it with which it is linked among itself, make be the most complex to modify one of these blocks above, it is exponentially complex because to create one of these blocks, it is necessary to solve a work test.