The question is how will you explain blockchain technology to a newbie and I see the challenge too but I'll go like this...

Blockchain is basically a technology that allows peer to peer transactions (and these transactions can be anything from paying for services to certifying homeownership, to verifying credit scores) without the need for any 3rd party authenticator. For example, in paying for services with your credit card, you need the banks as 3rd party authenticators, for certifying homeownership, you need lawyers and county officials where your home resides as 3rd party authenticators and for verifying credit scores, you obviously need the credit scoring companies as 3rd party authenticators. Each of these authenticators demand fees, making this form of transacting quite expensive (who do you think pays for the bank's massive buildings and extravagant salaries and bonuses?)

Of course, the blockchain does require authentication but the difference with the blockchain authentication is that it is done by the crowd of blockchain users whose only incentive is to protect their own assets on the blockchain network (not any payment for being external authenticators). This has 2 profound implications...

1. Using the blockchain for transactions will be significantly cheaper than via traditional methods and

2. Since incentives for authentication is aligned with one's interest or assets, there will be very little need for fraud or unethical behavior on the blockchain network like we've seen with banks selling junk assets to individuals just to increase their own bottom-line.