What are "Floaters" in the novel, What Happened to Lani Garver?

A Floating Angel is an angel that comes down from heaven in human form to take care of needy people on earth. They're called floaters because they float from needy person to needy person, dipping in and out of people's lives. Floaters look like humans - but they have no age, gender, or sexuality - rather than a heavenly figure so that humans won't know when they're around. Most of the narrative is concerned with convincing the reader that Lani Garver is a floating angel sent from heaven to care for Claire.