Horizons of the Vast is a new adventure path for Starfinder. If you're looking to create a character that fits in perfectly well with the path as well as get some info about what worlds your character will be adventuring through, you'll want to check out the new Player's Guide that Paizo has posted on their website.
From the website:
“Welcome to Project: Horizon! As part of this onboarding seminar, we’ll be exploring some of the challenges you should expect to face when administrating your first charter, discussing the backgrounds that made you ideal choices for this undertaking, and reviewing some of the unique skills you might bring to the table or develop during your time in the Weydana system. We look forward to both your individual and collective contributions to Project: Horizon!”
Inside you will find answers to the questions, “What is Project: Horizon” and “Why us?” There are tips on how to prepare to be far from home where it can take several days, possibly weeks, for messages to reach your patron and for responses to arrive in turn. Find guidance on how to fill your roles as administrators, overseers, and managers of a slice of New Harmony, with all the responsibilities those roles entail. You can also find character options like The People’s Champion feat which enables you to draw confidence and dedication from the sheer number of people who depend on you. Or the new beastblood theme, described below.