The cops finally have memories
In almost every GTA game, the police have total amnesia. You can blow up thirty cars on a Tuesday, go to sleep, and on Wednesday a cop will just give you a warning for a minor traffic accident. It doesn't make a lot of sense. Rockstar seems to be pushing for extreme realism with GTA 6, and a lot of rumors point to the VCPD actually keeping a permanent file on you.
Basically, the game engine will quietly keep track of the types of crimes you are committing as you explore the open world. It is your permanent rap sheet.
How it changes the game
The biggest thing this profile affects is how fast the cops escalate things. Let's say your profile flags you as a highly dangerous, violent offender because you love using rocket launchers on the highway. The next time you get a simple one star wanted level, the cops aren't going to hold back. They will probably jump straight to using lethal force because they know exactly who they are dealing with.
But on the flip side, if you play more like a professional thief who only steals parked cars and runs away from fights, the police might treat you differently. They might prioritize using tasers and roadblocks to arrest you peacefully instead of just shooting you on sight.
Does the world react to you?
It will be really interesting to see if this leaks into normal gameplay too. In Red Dead 2, Arthur's honor level changed how random people in town talked to him. If you have a horrible criminal profile in Vice City, maybe shopkeepers will lock their doors when they see you walking up to the glass. We don't know for sure if you can wipe your record clean, but I bet doing legit jobs or bribing the right officials will help you lay low and reset your profile over time.