What is mean for()

Answer 1

Review the lessons, all the answers are there.

Answer 2

input and print are functions.
When you run function name followed by parentheses, a function call is performed.

When you call a function they will perform some tasks, which is basically just a block of code that will be run.

Functions can return values, when called function returns values to the position where the function is called.
input is a function that returns a string based on what user entered.

Functions can also take arguments, that are values passed for function parameters, which work like variables in function's code block when the function is called.

print function prints its arguments.

In Python functions work like any object, you can store them in lists, variables and call them.
func(args) -> return value
func -> function self

qunc = func
qunc(args) -> return value

punc = [func]
punc[0](args) -> return value

Answer 3

In python, for iterates through some iterable