Example 1
Norman has impressed his pub trivia team with his knowledge of 80s hair-metal bands.
We use the present perfect form of the verb impress here because Norman currently exists as an authority on Bon Jovi, Ratt, and Quiet Riot. The action of impressing his teammates was completed in the past, and his current status, right now, is that of somebody who has previously demonstrated his deep understanding of backcombed hair and leather pants.
Example 2
Carolina had planted three rows of tomatoes in her garden before the tornado swept them all away.
Since Carolina completed the action of planting tomatoes in the past, before the tornado stole them, we use the past perfect form of the verb plant. Now if only she could click her ruby slippers together and magically summon her missing tomatoes.