'*args' keyword allows to pass a variable number of arguments and arguments are stored in a tuple.

'**kwargs' keyword allows to pass variable number of arguments in a function and store the provided arguments in tuple.

Functions in programming:

1. allow modular approach
2. improve program readability
3. help in code reusability
4. All of these

The structure of function header in Python is:

1. "def" keyword followed by the function name and parameters
2. "func" keyword followed by the function name and parameters
3. "def" keyword followed by the return type, function name and parameters
4. "define" keyword followed by the function name and parameters