Imagine you have a blender. To your blender, you add a couple scoops of ice cream and some milk. Then you press the buttons on the blender. Soon, you have a delicious vanilla milkshake. Next, you add strawberries and press buttons again. The result is even better than before: a strawberry milkshake.
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Of course, strawberries aren't the only option. Suppose that, instead of strawberries, you added cocoa powder and avocado. The result is a chocolate-avocado milkshake. Or you could have added some mint leaves, for a mint milkshake. Or some peaches, for a peach milkshake.
In each of these cases, you pick the ingredient, and get a different milkshake. Whatever ingredient you pick, the result is always a milkshake. In other words, the blender took your ingredients, and returned a flavor of milkshake.
The blender is like a function.
