its actually not that hard to explain

Block chain -open ledger of all transactions on said network( each person gets a copy when they download a wallet, each transaction must be confirmed, by others in the network, to go through)

currencies- monetized incentive for maintaining said Block chain network via mining, staking or masternode

mining -essentially you're performing maintenance checks and turn the transaction info into blocks to be sorted on the chain

staking -like a saving account (adds interest) as long as you are connected to the network( insuring network connectivity)

masternodes- always connected to the network verifying transactions for the miners to add to the network block chain 

if they are not good with tech terms use business terms(most people understand them)