Your game database will carry across in its entirety from FM23 - so player historys, CA/PA etc. So, your all the players and staff in your FM23 world will enter FM24 in the exact state they were at the point you saved the game last in FM23.
As I understand, the only thing that won't carry across is the match highlights, goals etc. So you won't able to load any matches played in FM23 to see the goals etc, once the save has been loaded into FM24.