"It" is a pronoun in English that is used to refer to a thing previously mentioned or easily identified in the context. It's often used to denote an inanimate object, a concept, or even a situation. For example, when someone says "It is raining," the word "it" refers to the weather condition known as rain.
The word "it" comes from Old English "hit," which is a neuter singular pronoun. Its usage has evolved, but it has retained its role as a pronoun used for referring to non-human entities.