A blockchain is automatically linked to a currency or what is called a token which is programmable. For example, Bitcoin is a programmable currency.
We group together in block form all the transactions made by the actors of the network. The miners that form the nodes of the network validate these blocks, with conditions specific to that of the blockchain. This is the type of the blockchain that will determine how the blocks will be validated. This can be PoW, the Proof of Work, which is used in this case by Bitcoin. In this method, algorithmic problems will then have to be solved by the GPU or the ASIC.
Each block that has been validated will receive a date and time. It will then be added at the end of the chain of blocks. The entire network, just like those who receive the channel can finally see this last exchange.
In summary :
1 - Robert makes an exchange to Julie,
2 - Grouping of several exchanges in a block,
3 - The nodes of the network validate this block thanks to cryptographic techniques,
4 - The block is dated, then added to the chain,
5 - All users can view this block at the end of the blockchain,
6 - Julie receives Robert's exchange.
This transactional method takes some time depending on the type of blockchain used by the crypto currency. This can range from a few seconds to about fifteen minutes.