Simple past tense is linguistically indicated by an inflection on the base form of an infinitive verb: to drop, dropped; to learn, learned or learnt (irregular verb are handled differently: e.g., to run becomes ran). It indicates actions already completed in past time: I dropped the vase yesterday. I learnt that last week. I ran last track season.
Past perfect is linguistically indicated by the past tense combined with the perfect aspect. Aspect differs from tense. Tense shows the occurrence of an action in time. Aspect shows whether an action happens once or repeatedly. Aspect shows whether an action is completed or continuing. Past tense perfect aspect (past perfect) shows that an action is completed by a specific time in the past: I had watched it. You speak in the present about a past event that was completed by a specific time (unstated or stated) also in the past.
To elaborate upon the example for the sake of illustration: I began it on Saturday two weeks ago and I had watched it by the next Thursday. The speaker is in the present referring to a completed action begun in the past and completed at a specific time in the past.
Excellent answer to a question that probably should have been posted on the Question and Answer board. Nice job Frizzy. however, enotes has some other grammar resources abvailable at the following link.
The use of the SP is self explanatory. It is a basic reference to a finished past event. Eg...
I crashed my car yesterday.
The meal was a disaster.
The Normans invaded Britain in 1066.
The PP is normally for refering to an event which took place before a second, subsequent past event.
The Romans had conquered most of the Mediterranean before Julius Cesar became emperor.
They had written to the President more than fifty times before they finally received a call from a junior Whitehouse intern in May 2009.
It is also used as an introduction to a story, or to give background information...
We had gone on holiday to Turkey to relax and unwind.
The Palestinians had hoped that these meetings would restart the peace process.