Perfect tenses: Present and Past

PRESENT PERFECT:  Expresses an activity or situation that happened in the past and is connected to the present moment.

FORMULA: subject + have/has + participle + complement

We have traveled to the Grand Canyon many times.
I have eaten hamburgers every day this week. 

PAST PERFECT: Expresses an activity or situation that happened before a specific time in the past.  It has no connection to the present moment. It is often locked in the past with words like “before”.  

FORMULA: subject + had + participle + complement

My grandfather had traveled to the Grand Canyon before he died. 
I had finished my homework before playing video games.

Here are some handy guides to visualize these tenses in action...