Patina is like the color on a penny or a statue that's been outside for a long time. When things are outside, they get exposed to air, water, and different kinds of weather. Over time, these things can change the way the object looks. Some people really like the way things look after they've been outside for a while, and they call it "patina". It's like the object has its own special history that you can see just by looking at it.