It (sometimes capitalized as IT), more commonly known as Pennywise the Dancing Clown, is the titular main antagonist of the novel, its 2017 film adaptation and the 1990 TV adaptation. It was portrayed to be a shapeshifting and malevolent entity millions (possibly billions) of years old, and with no exact gender or solid identity; thus why it is called "IT".
It was a mysterious evil being from an unknown realm/dimension outside the regions of space. When It came to planet Earth to feed, It's favorite disguise was that of a colorful and wisecracking circus clown named "Pennywise". It could also morph into any other being or thing it pleased, generally based on its target's loved ones or friends to lure them into traps or simply appear to them as their very worst fears and nightmares.
It preferred to attract children, so it could capture and kill to devour them. It was capable of killing every kind of human but mostly preferred to prey upon innocent human children because they were easier to manipulate and scare. According to the creature, frightened flesh tastes better.
Lists Featuring Pennywise
Top Ten Scariest Movie Creatures and Villains of All Time Scariest Faces In Horror Movies
Best Horror Movie Villains Top 10 Clowns You Don't Want To Mess With
Top 10 Stephen King Villains Top 10 Scariest Movie Clowns
Top Ten Fictional Characters to Dress as for Halloween Top Ten Movie Villains of all Time