The past tense (1)

(i) To show an action that took place or happended at a certain time in the past.

Example :

1) I bought a computer yesterday.

(ii) To show a past habit with words such as 'often', 'always', 'never', 'seldom' and 'sometimes'

Example :

1) When I was a boy, I often caught spiders with my friends.

(iii) We use 'did' + infinitive in the negative and interrogative forms in the simple past tense.

Example :

1) Did Tom visit the dentist yesterday?

Tom did not visit the dentist yesterday.