Blockchain is the technology of distributed Peer-To-Peer public network, which can permanently and irrevocably store information about transactions (deeds), which are cryptographically secured.
The first known blockchain system is Bitcoin that was launched in 2008 and originally is applied for cryptocurrency of the same name.
Second-generation blockchain networks can provide multiple options for different purposes: creating smart contracts, smart property, voting, storing legally significant actions wich timestamp and so on.
People are free to add their nodes to the network and to provide their computing resources to the needs of such network and are rewarded for performed work.
Blockchain provide unprecedented high level of protection of information and allows do create entirely decentralized systems.