There's been some confusion about this, but Sony clarified today in a blog by specifying the number of games, and that it's at launch/day 1.
So it's basically full backwards compatibility Day 1.
With the exception of these 10 games:
Afro Samurai 2 Revenge of Kuma Volume One
TT Isle of Man - Ride on the Edge 2
Just Deal With It!
Shadow Complex Remastered
Robinson: The Journey
Hitman Go: Definitive Edition
And all the digital games you purchased on the PSN store carry over to your PS5.
That's pretty huge.Last edited by Hiku - on 09 October 2020