I know that the list() constructor creates a new list but what exactly are its characteristics?
What happens when you call list((1,2,3,4,
Your question is vague, but this is the output as follows, it doesn't "replace" the outer braces, it creates a data structure of a list, that can contain any value in a "listed" order (one after the other, after the other, and so on...) in a recursive way, you can add/remove elements to a specified index using append and pop. By the other hand, tuples are static and are not dynamically linked, they are more like an array of any type of element.
WHEN:
list((1,2,3,4,[5,6,7,8],9))
RETURNS:
[1, 2, 3, 4, [5, 6, 7, 8], 9]
WHEN:
list([[[2,3,4]]])
RETURNS:
[[[2, 3, 4]]]
WHEN:
list([[1,2,3],[4,5,6]])
RETURNS:
[[1, 2, 3], [4, 5, 6]]