What is temp ?

Question

double temp = 4.25;

Answer 1

Temporary variables are usually named "temp". It's just like any other name and doesn't affect the variable and is only for readability.

In your case it's a variable of type double initialized to 4.25.

Answer 2

temp is a variable of type double.

Answer 3

Try to avoid variable names like temp though, unless absolutely necessary. Variable names should be human readable.

e.g. car_colour = 'red'
rather than c = 'red'

This makes the code more readable and therefore reduces the probability of bugs, and makes the code more maintainable.