I, for one, start by explaining that it's a new form of money, based on pure Math, with no central authority and no need to trust anybody anymore. Then I continue with a comparison between fiat money and BTC, emphasizing how, while in case of fiat you have to trust banks and governs, in BTC's case you don't have to reply on anybody anymore. I continue by saying that, while fiat can be printed over and over, BTC has a limited quantity. Then I explain the difference between the inflation of fiat and deflation of BTC. Then I explain how, in BTC's case, there is nobody on this world to stop you from pressing "Send" from your wallet's menu.

I remind that bank accounts may always be frozen by banks, while BTC kept correctly, in your non-custodial wallet, can never be frozen by any entity. And, at this point, I explain the dangers some chose to face (knowing or unknowing) by using BTC in an inappropriate manner (centralized exchanges; centralized exchanges correlated also with bank accounts; KYC; hackers; identity theft etc.).

Then I explain how BTC is born, what is mining process and why it is similar to physical mining.

Then I talk about BTC's rarity and that, in time, its price should raise more and more, due to adoption and scarcity.

Then I take a break and I ask that person what questions he has. Then I answer calmly to all his questions... In the end I suggest some materials for reading.

This is how I introduce Bitcoin to a regular person.