Both Stephen King's novel It and its titular character have deep meaning worthy of exploration and analysis.
It is known by several names throughout the novel, including Pennywise and Bob Gray. It is a shape-shifter and is able to take on different physical appearances. One of It's favorite personas is a clown named Pennywise, but It is also fond of assuming the form of whatever its victims fear most. It's many aliases and ability to change forms are likely contributors to the selection of its name: since it is not one specific thing, but many things, King appropriately names it It.
It is an ancient creature that feeds on fear. This explains why It's favorite victims are children, as children are more vulnerable and prone to fear than adults are.
There are several interpretations of It that would be interesting to examine and analyze in your essay. Here are a some ideas to get you started.
It is the vehicle through which the Losers are able to confront and overcome their trauma. Bill is devastated by the loss of his little brother, George. He feels responsible for his brother's death, since he gave George the paper boat that led him to Pennywise and a brutal, untimely death. Beverly is abused by her father. Mike is subjected to racism and abuse. Ben is taunted because he is overweight. All of the Losers are bullied and traumatized at the hands of Henry Bowers and his friends. By assuming the forms of their worst fears, It enables the Losers to confront and overcome their respective and collective trauma.
It also represents the loss of innocence. The Losers are forced to mature prematurely because of their trauma and the threat of It. It unintentionally empowers the Losers by bringing them together and allowing them to access their previously untapped bravery, courage, and power. The Losers realize they are each strong in their own way and are strongest when they are together. This solidarity is what allows them to ultimately defeat It. Once the Losers lose their innocence and relinquish their fear, they are able to defeat their enemy by starving it of the fear it feeds on. The term Losers has a double meaning and refers not only to the Losers' status as social outcasts, but also to the loss of innocence they all experience.