did是do的过去式。do作动词意为“作”、“进行”、“从事”，do作为助动词可以构成疑问句和否定句，代替动词，用于加强语气。do作名词有“社交聚会”、“社交活动”的意思。

do的用法

1.do作助动词用法

（1）用于实义动词前构成否定句和疑问句

They didn't go to Paris.

他们没去巴黎。

Does she speak French?

她会说法语吗？

（2）构成附加疑问句

You live in New York, don't you?

你住在纽约，不是吗？

（3）代替实义动词以避免重复

He plays better than he did a year ago.

他的球比一年前打得好了。

（4）句中无其他助动词时，用以加强语气

He does look tired.

他的确显得很疲倦。

（5）副词移置句首时，用以改变主语和动词的语序

Not only does she speak Spanish, she's also good with computers.

她不仅会说西班牙语，还精通计算机。

2.do作动词

（1）What are you doing this evening?

你今晚打算做什么？

（2）They are free to do as they please.

他们想怎么做就怎么做。

（3）How is the business doing?

生意好吗？

（4）I'm doing some research on the subject.

我正就这一课题进行研究。

（5）I like the way you've done your hair.

我喜欢你梳的发式。

（6）What does she want to do when she leaves school?

她毕业后想干什么？