Edited:
I will explain the blockchain to a child as an unending train owned by no one, which carries gifts for people. Every child can always put their gift into the train according to each coach. Each gift is checked by different cameras which is viewed by different people in different part of the world. Whatever gift has been dropped into the train cannot be removed for life and no one can attack the train because it is guarded with electric wires.

I will explain the Blockchain to a novice as a register in form of blocks tied together in chains where information are inserted into each block by anyone. each block has a tally (hash) of the previous block and the next block so it can be easily identified by whoever drops data into it. The block is immune to attack as the content of the block is being certified by different people at the same time.

To be continued...