All finite, or conjugated, verbs in English express grammatical tense and grammatical aspect. Tense is the grammaticalized expression of the location in time of an action or state, which only roughly relates to actual time. Aspect is the grammaticalized expression of the temporal structure of an action or state, which roughly relates to duration.
Simple Present
The simple present expresses discrete actions or events in the present or near future. The simple present is most often used to express discrete actions or states in the present, habits and routines, general facts and truths, thoughts and feelings, and events in the near future.
The following visual illustrates the uses of the simple present of English verbs:
Simple Past
The simple past expresses discrete, completed, noncontinuous actions or events in the past. The simple past is most often used to express discrete actions or states in the past, past habits and routines, past general facts and truths, past thoughts and feelings, and noncontinuous duration in the past.
The following visual illustrates the uses of the simple past of English verbs:
Perfect
The present perfect expresses and emphasizes the consequences resulting from a previous action or state that began in the past and continued up to the present. The present perfect is most often used to express experiences, accomplishments, changes over time, uncompleted actions with expected ends, continuous actions with starting points in the past, past actions with present results, and multiple actions at different times.
The past perfect expresses and emphasizes the consequences resulting from a previous action or state that began in the past and continued until another previous action or state. In other words, the past perfect expresses an action or state in the past that occurred before another action or state in the past. The perfect past aspect is most often used to express a completed action that occurred before another action in the past and in sentences that express actions that began in the past and continued up until other actions in the past.
The following visual illustrates the uses of the perfect aspect of English verbs:
Progressive
The present progressive expresses an incomplete or ongoing action or state. The incomplete or ongoing action or state began in the past, occurs in the present, and continues into the future. The present progressive is most often used to express actions happening now, extended actions that are in progress, actions happening in the near future, repetitive and irritating actions, and actions occurring for a limited time.
The past progressive expresses an incomplete or ongoing action or state that began, continued, and ended in the past but over a longer period of time than the completed actions expressed by the simple past. The past progressive is most often used to express past actions that progressed in time in the past, that ended from an interruption including specific times, that occurred simultaneously, that describe the atmosphere, and that are repetitive and irritating.
The following visual illustrates the uses of the progressive aspect of English verbs:
Perfect-Progressive
The present perfect-progressive expresses and emphasizes the consequences resulting from a previous incomplete or ongoing action or state that began in the past and continues into the present but may or may not continue into the future. The present perfect-progressive is most often used to express actions that occurred recently and actions that continue up to the present.
The past perfect-progressive expresses and emphasizes the consequences resulting from a previous incomplete or ongoing action or state. The past perfect-progressive is most often used to express actions that continued for a duration of time in the past and actions that caused other actions in the past.
The following visual illustrates the uses of the perfect-progressive aspect of English verbs:
All conjugated verbs in English express tense, which is the grammaticalized expression of the location in time of an action or state but only roughly relates to actual time, and aspect, which is the grammaticalized expression of the temporal structure of an action or state and that roughly relates to duration.
References
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.