Snoop Snoo is a Reddit analytics tracker that boasts the phrase "You are what you post," and it's not kidding!
When a username is inputted into the finder it pulls up a profile based on the posts created by that user. It'll say if you're dating, married, have siblings, what shows you like to watch, what jobs you have, etc.
It can get downright creepy as it pretty much lays out exactly who you are based on the comments and submissions you've made on your profile. However, it's not the most accurate thing on the planet.
For example, let's say you're user u/RamsesThePigeon, who's known for writing fictitious comments:
There's a soft blend of fiction and non-fiction, but since each data point has the corresponding post it gleaned the information from linked. You can easily double check the information.
It can be pretty creepy to anyone who doesn't know how much information they've posted to the site.