Final answer:
In Python, the index refers to the position number of a piece of data within an ordered collection, such as a list or tuple. Python utilizes zero-based indexing, starting at 0.
Step-by-step explanation:
In Python, the index is the position number of a piece of data within a list, tuple, or other collection type that is ordered. For example, in a list my_list = ['a', 'b', 'c', 'd'], the index of 'a' is 0; the index of 'b' is 1, and so on. Python uses zero-based indexing, meaning that the first element in a sequence has an index of 0, the second element an index of 1, and so on. It is essential when you are trying to access individual items in a sequence. If you need to access the last item in a sequence, you can use a negative index, such as my_list[-1], which would return the last item 'd' in the provided list example.