My first temperature converter

[buran]

If I dont have the "return" and the cel, fah, kel, the program won't be able to return the calculation to convert the temperature type and the number that the user had input

Note I refer only to displayResults function.

def displayResults(cel, fah, kel):
    print("Celsius =", cel)
    print("Fahrenheit =", fah)
    print("Kelvin =", kel)
    return cel and fah and kel

Your function just prints the arguments you pass. It does not need to return anything, nor you use what it currently returns. On line 65 you just call it displayResults(cel, fah, kel). You don't assign what it returns to anything and simply throw it away.

Now the other problem, look at the return statement:

return cel and fah and kel

cel, fah and kel are floats. So if all 3 variables can be evaluated as True, it will return kel. If any of cel or fah is 0 or 0.0, i.e. that is evaluated as True, it will return it.

>>> 1 and 2 and 3
3
>>> 1 and 0.0 and 2
0.0

read more here https://docs.python.org/3.8/library/stdtypes.html#truth