What do * and ** before function arguments mean?

The use varies whether it used in function header or while calling any function.

Inside function header

The * and ** inside function header mean:

• * collects all the positional arguments in a list or tuple.
• ** collects all the keywords arguments in a dictionary.

Inside function call

The * and ** inside function header mean:

• * unpacks list or tuple into positional arguments.
• ** unpacks a dictionary and assigns as keyword arguments.

References

• Stackoverflow