The past simple functions similar to Present simple, except that we use the auxiliary 'did' to all persons (including the third person singular 'he / she / it'). In the affirmative, the assistant 'did' does not appear, instead using termination 'ed'. This is the way past for all 'Regular Verbs'
There is a broad set of verbs that do not meet this condition, ie how to use affirmative termination 'ed' but its shape is irregular. There are still no hard and fast rule, so the only way to know their past is how to learn. They are called 'Irregular Verbs
For past actions. Indicate the period of time that was developed and completed an action already complete. Typically accompanied by an adverb of time.