system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How do genealogy websites that are used to reveal your family tree work? Do they work as well as advertised? Who is compiling all of this information?

I have friends who use these websites (they're pretty common so I don't think I need to list any names) and they seem to work pretty well to my surprise. What I don't understand is how they work, and who's job it was to compile this data.
gpt
A lot of genealogy is compiled by Mormons but marketed as a standard family history site. They use the data they find to posthumously baptize people into the church.

I would also assume companies do it for the monthly subscription fees.