The simple past is used for events that began in the past, ended in the past, and happened at a time that is known. The present perfect is used for two things: for events that happened in the past but we don’t know when or the time is not specific, and events that started in the past and continued until the present.
A series of simple past tenses can be used to describe several things that happened in the past at the same time or in sequence. The emphasis in the present perfect is on how events and states in the past relate to and affect the present. The first sense of the present perfect is frequently used with the words “ever” and “never,” to ask about events from any point in the past or in a person’s life. The second sense of the present perfect is frequently used with “for” or “since” to talk about the duration of events and states which began in the past and have continued until the present.
Be careful: tenses comparable the the present perfect do not exist in many languages, and choosing when to use these tenses in English can therefore be confusing. Also, while simple tenses need to have a specific time attached to them, this time can be described with an indefinite phrase, such as “when I was younger” or “several years ago.” They do not need to have a date or time.
|Simple past||Present perfect|
|I lived in Boston for three years. (finished)||I have lived in Boston for three years. (unfinished)|
|He went there in 2014.||He has been there. (I don’t know when)|