Sentences in the simple present and simple past have verbs consisting of just one word.
Study the following examples:

• The dog barks.
• The fire burns.
• I know the answer.
• He came.
• It works.
• She sang a song.

When the verb consists of just one word, the negative cannot be formed by putting not after the one-word verb. Instead, we use the auxiliaries do, does or did with not.

• The dog barks. (Assertive)
• The dog does not bark. (Negative)
• I know the answer. (Assertive)
• I do not know the answer. (Negative)
• He came. (Assertive)
• He did not come. (Negative)
• It works. (Assertive)
• It does not work. (Negative)
• She sang a song. (Assertive)
• She did not sing a song. (Negative)

Notes
Do is used in the simple present tense when the subject is I, you or a plural noun / pronoun.

• I write.
• I do not write.
• You work.
• You do not work.
• They play.
• They do not play.

Does is used in the simple present tense when the subject is a third person singular noun or pronoun.

• He sings.
• He does not sing.
• John writes.
• John does not write.

Did is used in the simple past tense with subjects of all number and person.

• She waited for John.
  She did not wait for John.
  I wrote a letter.
  I did not write a letter.
  The children sang a lovely song.
  The children did not sing a lovely song.

Note that did is followed by a verb in the present tense.

• She did not come. (NOT She did not came.)
• She did not wait. (NOT She did not waited.)

Related posts:

1. How to change a statement into a question
2. Uses of Do