From the DMs Guild page:
Welcome to the Fleshing Out Curse of Strahd: Player Primer!
This character chronicler was designed to inspire the creation of player characters for the Curse of Strahd campaign and includes documents for both Dungeon Masters and players alike.
Within this product, you'll find 4 different documents to help you prepare for the Curse of Strahd module:
Player Primer. Background information to help ready new players for their upcoming campaign and tables of player character backstory options to help them develop characters specific to the Curse of Strahd module. This document is spoiler free and player friendly!
Barovian Player Primer. This primer contains many of the tables found in the Player Primer, but rewritten to better suit a player character from Barovia. This primer is best used if you lose a player character to the horrors of Barovia and must introduce a new character to the party.
Character Options. 4 new race options suited to the Ravenloft setting: Dusk Elf, Vistani, Wereraven, and Werewolf.
Mysterious Secrets. 18 different secrets that can help integrate player character backstories into the Curse of Strahd adventure.
Since the publication of The Explorer’s Guide to Wildemount in March 2020, a couple different player primers have been published to help players integrate their characters into campaign settings. Most notably, we've seen the "Heroic Chronicle: Sword Coast and the North", which helps integrate characters generally into the Sword Coast, and the Player Primer: Icewind Dale, which helps develop characters specifically for the Icewind Dale: Rime of the Frostmaiden adventure module.
This primer was designed specifically for the Curse of Strahd campaign, to similarly assist in the character creation process. It reflects ideas and tables found in the previously mentioned work, but all rewritten to better suit the Ravenloft setting. With this set of campaign supplements, players should be able to develop characters that not only have depth and thriving backstories, but are also aimed towards the upcoming adventure.