This is used to express an action completed in the past. It often occurs with adverbs or adverb phrases of past time. eg. I received the gift two days ago.
Sometimes, it is also used without an adverb of time, where time may be either implied or indicated by the context. eg. I didn't sleep well.
Past Continuous Tense - definition
This tense is used to denote an action going on at some time in the past where the time of action may or may not be indicated. eg. We were listening to the radio all evening.
This tense is also used with always, continually, etc. for persistent habits in the past. eg. His grandmother was always grumbling.
Past Perfect Tense - definition
This tense describes an action completed before a certain moment in the past eg. I had met with an accident in Bangalore.
If two actions happened in the past, it may be necessary to show which action happened earlier than the other. In such cases, one clause takes the past perfect tense while the other takes the simple past tense. eg. I had completed my work when Sheena arrived.
Past Perfect Continuous Tense - definition
This tense is used for an action that occurred before a certain point in the past and continued up to that time. eg. At that time, he had been writing a novel for two months.