An object is a black box, which you can't see through. Public methods are buttons on them. Protected methods are buttons hidden on the bottom, private methods are dip switches inside.
Let's see a washer as an object. We don't know how it works. We don't care if it's powered by natural gas, diesel, electricity, or plutonium. However, the mechanism and internal structure will vary greatly depending on the energy source like a combustion engine is needed for some. We don't care as long as if we push a "Wash" button, it washes our clothes.
Let's turn the washer not Object-oriented. Expose all the buttons by arranging them on the top. Customers can now turbo-charge the engine by tweaking some dip switches. Make the chassis transparent. Now, you can see your energy-saving washing machine is actually hybrid-powered. There are some monkeys in it. You free them into the wild, and the machine eats up your utility bill like a gas-guzzler.
