He scares them and then kills them. This process seems to capture them in some fashion, presumably in his deadlights, which are closer to his true form. It seems like he doesn't enjoy killing those who aren't afraid of him, or perhaps he only has power over those who are afraid of him.
In both the book and the films, It is an ancient alien creature, older than civilization, and in King's novel, older than our universe. It feasts on the flesh of humans simply because our fears are easy to manifest and they make us taste better.
The added horror of killing someone so young and innocent immediately established Pennywise as a terrifying villain. Georgie's murder was also particularly brutal; after taunting him, Pennywise bit off Georgie's arm, allowing Georgie to helplessly crawl away before dragging the boy back into the sewer.
Unlike many horror monsters before him, It is not against killing children; in fact, the scary monster actually prefers to kill children as they are an easier target, and this is probably why he chooses the form of a clown, a figure that both entertains and terrifies many young children.
It lives in the sewers of the New England town Derry, awakening every twenty-seven years to prey on the town's children, feeding on their fears and using the writhing bright orange lights that comprised Its own life essence and is Its true form, known as "the Deadlights", a dangerous eldritch form of energy (which is ...
And if his victim believes him to be powerless, he will become powerless. And so the group figures out that their best bet is, essentially, to bully the bully: They mock Pennywise, telling him he isn't scary. Humiliated, Pennywise begins to shrink, transforming into an almost Benjamin Button–like, melted clown-baby.
A common interpretation of this phrase is that it refers to where the souls of IT's victims go after they die, as they wouldn't go to heaven nor hell, staying instead in the “deadlights”, which would be a sort of limbo, thus “floating” in that middle point for eternity.
They reach the conclusion that Pennywise has all of the adults under some sort of spell that prohibits them from seeing him. The adults of Derry are shown to be villainous in their own right as well. The adults of Derry are shown to be true villains of the story in the same way as Pennywise.
Stephen King's IT introduced readers to a one-of-a-kind creature that can take any form, the most common one being Pennywise the Dancing Clown, and as menacing as it is, this creature has one big enemy it's truly scared of: Maturin, the turtle.
However, he doesn't seem to target adults like he does kids, which is odd, seeing as how, as many will agree, adults have just as many fears, worries, phobias, anxieties, and insecurities as any child, maybe more since they've lived longer and thus had more time to develop more things to be afraid of.
Pennywise offers Georgie his boat back, but when Georgie attempts to reach out to it, Pennywise grabs Georgie's arm and bites it off, leaving Georgie to bleed to death in the rain.
A neighbor witnesses his disappearance, but the fact his body is never found gives Bill hope Georgie somehow survived. Pennywise prays on this in the film, using that hope to lure Bill in the finale. Bill later finds the tatters of Georgie's coat and finally accepts his brother is gone.
Then, when Georgie reaches in for his boat, you can feel how nervous he is. Finally, Pennywise tears off Georgie's arm to make sure Georgie knew he was going to die.
The character is an ancient, shape-shifting, trans-dimensional evil entity who preys upon the children (and sometimes adults) of Derry, Maine, roughly every 27 years, using a variety of powers that include the ability to shapeshift, manipulate reality, and go unnoticed by adults.
The backstory of Pennywise is tied to an ancient cosmic entity referred to as the "It" or the "Eater of Worlds." This entity is from another dimension and has existed for an extremely long time. It comes to Earth approximately every 27 years to prey on the children of Derry.
It was said on page 1361 that the Spider being both female and pregnant was a symbolic interperetation. Its not literal, but a representation of whatever equivalent but inconceivable reproductive capability It actually has. Pennywise didn't become pregnant.
In the novel, It's origins are nebulous. He took the form of a clown most frequently, Mr. Bob Gray or Pennywise, but his true form is an ancient eldritch entity from another universe who landed in the town that would become Derry by way of an asteroid and first awoke in 1715.
Throughout Stephen King's It, Pennywise is referred to as a male, but author Stephen King pulled a fast one on readers in the It book ending by revealing the creature's true form was a pregnant spider, implying that it is, in fact, biologically female.
IT arrived on Earth through an event similar to an asteroid impact, landing in what would later become Derry, Maine. Once there, IT adopted its usual pattern of hibernation that lasted between 27 and 30 years, awakening to kill and eat and then going back to sleep.
Pennywise targets children instead of adults because they are easier to scare and manipulate. Their fears are often simpler, more direct, and easier for Pennywise to exploit.
IT is a shape-shifting creature known as a Glamour who is billions of years old. Although it lived on planet Earth for many years, Pennywise originated in a void/dimension outside the regions of space known as the Macroverse.
Finally, Pennywise tears off Georgie's arm to make sure Georgie knew he was going to die. Does Pennywise (IT) have to eat and kill only children? No, that's a common misconception, IT only prefers to hunt children because they taste better and IT has more fun with their fears.
