The restaurant is trying to attract more customers, and the new menu is an important 'piece of the puzzle'. [=an important part of what is being done]
Ecologists no longer view different species as independent, but instead see them as pieces of the same 'jigsaw puzzle'.
His strange behavior is a 'puzzle' to his friends. [=his friends don't understand the reason for his strange behavior]
(..) to my gallery.* *I'll play guitar, and knit, and cook and basically.* *Just wonder when will my life, begin.* *Then after lunch, it's puzzles, and darts and baking.* *Papier-m'ch', a bit of ballet, and chess.* *Then I'll stretch, maybe sketch. (..)2010 Tangled