You get to play through the game as if it were the full game, but only for 30 minutes. After that the Demo is gone.
https://blog.us.playstation.com/2019/01/08/the-resident-evil-2-1-shot-demo-hits-ps4-january-11/
https://www.youtube.com/watch?v=h1f17VqIA_E
It'll be available between Jan 11 - 31, 2019.
Last edited by Hiku - on 08 January 2019