It is easy to recognize a person's face but difficult to understand their true character; do not trust people too easily. This idiom is often used with [[画虎画皮难画骨|画虎画皮难画骨|hua4 hu3 hua4 pi2 nan2 hua4 gu3]].

intimate words from the heart shared with a close friend

An intimate or bosom friend who understands and empathizes with one's feelings.

intimate friend; a person one can have a heart-to-heart with