Function:

1. Use the simple past to talk about an event that happened at a specific time in the past.  Also, to describe routines in the past, or to talk about events that happened after another event in the past.
2. Use the present perfect to talk about an event that happened sooner as it was expected, to ask a question about whether something has happened, and to talk about an action that has been in progress for an amount of time, a very recent past, or an action that began in the past and will continue in the future.