are you referring to the new “Privacy Sandbox” or the old “Privacy Sandbox”. because if there calling this new thing a “Privacy Sandbox” after the old one lost public attention after they kept promising it for years, I am going to laugh or maybe cry.
what they originally called “Privacy Sandbox”
it was a browser feature to remove the HTTP cookie and replace it with a cohort system.
your browser would receve signals about your habbits. that you were buying domino's pizza and announce to upcoming sites that you like pizza, but ya know... in a "safe" way.
I still see, "chrome is going to replace the cookie" and "RIP the humble cookie" every once in a while.