Blockchain technology allows two actors in the system (called nodes) to transact in a peer-to-peer (P2P) network and stores these transactions in a distributed way across the network.
Sources: Back, S. A., Corallo, M., Dashjr, L., Friedenbach, M., Maxwell, G., Miller, A., Poelstra, A., Timón, J. and Wuille, P. (2014). Enabling Blockchain Innovations with Pegged Sidechains. OpenScienceReview
ELISE Resources: Blockchain for Digital Government