The Past Perfect describes actions that were completed before another action or point in the past. It helps us break the "linear" approach of the Simple Past and adds complexity to our storytelling

We use the auxiliary verb "had" followed by a verb in past partriciple (e.g., had eaten, had gone, had seen). 

For example:

• By the time he arrived, they had already left. He was really late!

• She realized she had forgotten her keys at home.

Check the presentation below to learn more about this structure.