If you need to explain quickly what playing D&D is like to a clueless party, then I have found some entirely perfect links:
Adventure Time Episode 18 "Dungeon" (hit "continue as free user" after a few seconds)
A boy and his talking dog go into a dangerhole in order to overcome a self-imposed challenge and are aided by a very impatient pink-haired princess.
The parallels with my own game and existence are terrifying.
There is almost nothing in this that is not exactly like D&D.
This is what everything else about D&D, besides playing D&D, is like.
Bonus utility: Next time some smarthole asks you what brand of Fantasy Adventure Literature exactly is D&D meant to be simulating send them right here.