The phrase often implies a deep emotional bond with a place that feels comforting, regardless of its location. She felt at home in the cozy cafe she visited abroad; home is where the heart is.
Pro Tip 2/3
Metaphorical Use
It's used metaphorically to mean that 'home' isn't a physical space, but where you feel love and joy. As a traveler, wherever I hang my hat and feel loved, that's where I'm home - home is where the heart is.
Pro Tip 3/3
Expression of Contentment
It implies contentment with one's situation or location, because of emotional fulfillment. Living in a small apartment with his cat, he realized home is where the heart is.