You use they to refer to a group of people, animals, or things.
Feed the dogs because they haven't eaten.
喂喂这几条狗,因为它们还没吃东西呢。
The two men were far more alike than they would ever admit.
这两个男子非常相像,尽管他们可能不愿意承认。
People matter because of what they are, not what they have.
人的价值在于他们是什么样的人,而不是他们拥有什么。
You use they instead of 'he or she' to refer to a person without saying whether that person is a man or a woman. Some people think this use is incorrect.
The teacher is not responsible for the student's success or failure. They are only there to help the student learn.
教师不为学生的成败负责。他们只是帮助学生学习而已。
You use they in expressions such as 'they say' or 'they call it' to refer to people in general when you are making general statements about what people say, think, or do.
They say there's plenty of opportunities out there, you just have to look carefully and you'll find them.
人们说那里有很多机会,你只要仔细寻找就能发现机会。