Simple tense is that part of tenses where the verbs simply tell the state of an action depending upon the time of an action.
In Simple Present Tense the verbs state an action which is happening regularly. Eg: Ramu goes to school every day.
In Simple Past Tense, the verbs state an action that has been completed. Eg: I ate an apple.
In Simple Future Tense, the verbs state an action that will be performed in the future. Eg: He will visit the National Park tomorrow.