Blockchain is a fancy word nowadays but a pretty complex concept to explain in plain words.
It all comes down to applied cryptography, distributed storage (the Distributed Public Ledger) and consensus network: multiple synchronized copies of encrypted past transactions are packed into practically non corruptible blocks of data, distributed amongst non cooperative computing power units that compete to maintain the Ledger and validate new transactions, avoiding centralized approval mechanism, and being rewarded with strange units of values called digital tokens or crytpocoins.
But let’s take this away: a blockchain is a interconnected series (i.e. a chain) of blocks of data that contain past transactions occurred between network participants.
These blocks are time stamped and cannot be modified without breaking the chain, thus making the attempt to corrupt the blocks (e.g. fake transactions), in theory, impossible (i.e. insanely expansive).
REALTHIUM is built on the Ethereum’s blockchain, and the basic reason for this is that plenty of teams around the globe are working hard to make the Ethereum environment more friendly to distributed applications (Dapps) developers.