When I go to search someone’s name in the search bar on Facebook I can’t find them but I’m able to find their them on someone’s friends list?

[Anonymous]

but can’t find it by searching for their name on a person’s friend’s list. What does this mean?

[treesareold4]

Maybe they have there profile on some type private, I'm not really too sure though. I could be a search error that's just not working right.