Blockchain is a technology which firstly used in Bitcoin and then other cryptocurrencies. Blockchain is basically a host for keeping datas.
For understanding Blockchain's purposes better, we need to look at current banking systems. Banking systems generally use a closed data system and no one is able to see transactions. But Blockchain serves the purpose. It's a open system to everyone; it's transparent, decentralized and it doesn't need any intermediate structures. Let's take a look closer:
Block: Each block stores some data, hash of the block and hash of the previous block.
Bitcoin's data for example, contains transaction informations such as: from who, to who and amount of BTC. Hash is ID of the block and every block has unique hash, it's basically like our fingerprints. And the hash of the previous block is the chains. It allows to connections of blocks.
P2P Network: This is the technology that provides secure and making distribution.
When someone joins network, system gives him, her full copy of blockchain. If someone creates a block (makes a transaction), system sends it to everyone on the network. And thus system works perfectly and verifies everything in order.
