Can someone please explain me why the "-1" in this line "max_index = len(words) - 1"

Question

words = ["hello", "world", "spam", "eggs"]
counter = 0
max_index = len(words) - 1

while counter <= max_index:
word = words[counter]
print(word + "!")
counter = counter + 1

Answer 1

since there are 4 words Len returns 4 but the individual variables are numbered 0,1,2,3 making the highest variable 3, that's all I could gather

Answer 2

exactly, len() built-in returns the size of the object passed as arg. which can lead you to an error if you need the max index of a list, because lists are like arrays and always start at index 0