1、作实义动词，也叫形为动词。和普通的动词一样，有自己的实际意思，表示“做”。
例如：do 、homework, do exercises等。
当主语是I/We/You/They或者复数名词时，动词用do。
例如：I often do my homework in the evening .
当主语是He/She/It或者其他单数名词时，动词用does。
例如：
She often does homework in the evening .
2.作助动词，无实际意思。通常用于疑问句和否定句。
(1)用于一般疑问句。直接在句首加上do/does，注意大小写和部分人称及动词的变化。
例如：
I like apples.
Do you like apples?
Yes, I do. /No, I don't.
当主语是三人称单数时，用does.
例如：She likes apples.
Does she like apples?
Yes, she does. /No, she doesn't.
(2)用于否定句时，在句子中加上don't或者doesn't.
例如：I don't like apples.
She doesn't like apples.