Whenever I try to explain bitcoin to my friends, I never go like this : "Bitcoin is a cryptocurrency and worldwide payment system. It is the first decentralized digital currency, as the system works without a central bank or single administrator. The network is peer-to-peer and transactions take place between users directly, ... bla bla bla"
Source : https://en.wikipedia.org/wiki/Bitcoin
Instead I just show them this Hilarious video that I found on youtube.
In case you haven't watch this, I grantee you it's brilliant and worth three minutes of your time.
Disclaimer: I don't own the video nor do I related to it in any way possible