The contact then has the ability to write a post to display at the top of the late user's timeline, respond to new friend requests, update the profile and cover photos and decided whether or not the profile remains online.
With permission, they can also download an archive of the posts, photos and profile information shared on Facebook.
However, there's no need to worry about embarrassing private chats being accessed in the afterlife - legacy contacts only have limited access to your profile and you can even decide to have it permanently deleted instead.
To set up the feature, open settings, choose security and then Legacy Contact at the bottom of the page. After choosing a contact, Facebook gives an option to message the user and let them know.
Just make sure you choose that contact wisely, as your online legacy could last forever.