it

The pronoun it is commonly used to refer to something without naming it. The plural pronoun they can be used to refer to multiple things in this way, as can the object form them.

The word it is sometimes used to refer to an animal, and in some cases it can refer to an unknown person, such as when someone knocks on the door and you ask “Who is it?” (Otherwise, though, referring to a person as it for any reason is extremely offensive.)

Most commonly, it is used to refer to things.

Like the word thing, the word it is usually the one being used in place of a more specific word. But there are other general terms you can use instead.

It can refer to anything—it can refer to physical objects or articles but also to nonphysical entities. The word item can be used for tangible things (as in That item is sold out) or intangible ones (as in Let’s save that item for the next agenda).

The words this and that can be used in place of it when referring to something that’s near, understood, or previously mentioned or indicated. They can also be used for emphasis. For example, instead of asking “What is it?” about some unidentifiable thing, you could ask “What is that?”

It is also very commonly used to introduce sentences that use a form of the verb be, especially statements about time (as in It’s five o’clock), distance (as in It is five miles away), or the weather (as in It was raining this morning). It is also commonly used in many similar constructions (such as in phrases like How’s it going? or Where does it hurt?). All of these can often be reworded to avoid using it, as in The time is five o’clock or There was rain this morning. However, constructions using it are often the most natural-sounding.

It is also used in some more specific ways.

In the children’s game of tag, the word it is used to refer to the person designated as the tagger, as in Tag, you’re it!

When a person is said to have “it,” this means that they possess some unique characteristic (often charisma)—sometimes known as the it factor. A girl (or, more often, a woman) who is newly popular in a certain arena might be called the it girl, as in She’s the new it girl in fashion. 

When capitalized, IT is a common abbreviation for information technology, which is sometimes also shortened as infotech. Another name for the IT department is the tech department.

Yes, it is a pronoun. The singular subject (nominative) and object form are both it. However, the plural subject form is they and the plural object form is them. The possessive form is its.