What are list slices? What for can you use them?

What does each of the following expressions evaluate to? Suppose that L is the list
["These", ["are", "a", "few", "words"], "that", "we", "will", "use"].

1. L[1][0::2]
2. "a" in L[1][0]
3. L[:1] + L[1]
4. L[2::2]
5. L[2][2] in L[1]

What do you understand by true copy of a list? How is it different from shallow copy?

Compare lists with strings. How are they similar and how are they different?