used as the subject of a verb, or the object of a verb or preposition, to refer to a thing, animal, situation, or idea that has already been mentioned

"Where's my pen? It was on my desk a minute ago." "You left it by the phone." “我的钢笔在哪儿？刚才还在我的桌上。”“你放在电话旁了。”

The company was losing money and it had to let people go. 该公司在亏损，所以不得不裁员。

The argument was upsetting for us all - I don't want to talk about it. 那场争论使我们大家都心烦——我不想再谈论了。

Children who stay away from school do it for different reasons. 孩子逃学有各种原因。

used as the subject or object of a verb to represent a phrase at the end of the sentence

It's unlikely that she'll arrive on time. 她不太可能准时到来。

It costs more if you travel before 9.00. 如果你在9点之前开始行程就会比较贵。

I liked it in Scotland. 我喜欢在苏格兰。

I find it convenient to be able to do my banking by phone. 我发现电话银行很方便。

used to talk about the time, date, weather, or distances

What time is it? 现在几点？

It was October, so it was quite cold. 那时候是十月，所以很冷。

It rained all day. 整天都在下雨。

It's ten miles to Leeds. 距利兹十英里。

used for describing things or people that are very fashionable, and everyone is interested in them, wants to have them, etc.

The design of this bag makes it the "it-bag" for this summer. 这款包的设计使它成为了今夏的潮流。