Built-in functions in Python are pre-defined functions readily available for use in any Python program without requiring additional specifications or definitions. One of the built-in functions is the print() function - we have already used it. We didn't need to define this function, write its body and specify the return value - we just called it and provided inputs. There are many built-in functions in Python. Now we will consider the most commonly used:

• print(): Outputs a specified message or variable to the console.
• len(): Returns the length (number of elements) of an object, such as a string, list, or tuple.
• type(): Returns the type of an object.
• input(): Reads a line of text input from the user.
• int(), float(), str(): Converts a value to an integer/float/string.
• sum(): Calculates the sum of a sequence of numbers.
• max() and min(): Returns the maximum/ minimum value from a sequence.
• round(): Rounds a number to a specified number of decimal places.

Let's look at the example:

Let's provide some explanations:

1. The function begins by checking the type of each input value using the type() function. If the type of a or b or c is not float, it is cast to a float using the float() function.
2. The calculation is then performed using the updated values of a, b, and c:
   • max(a, b, c) + min(a, b, c) calculates the sum of the maximum and minimum values among a, b, and c.
   • sum([a, b, c]) / 3 calculates the average of the values.
3. Finally, the division (max + min) / average result is computed and stored in the result variable which is a return value of the function.