String indexing: String indexing refers to accessing individual characters within a string using their corresponding index values. It allows you to retrieve specific characters based on their position in the string.
Substring: A substring is a smaller section or part of a larger string. It is obtained by extracting a specific range of characters from the original string using slicing.
Immutable: In Python, strings are immutable, meaning they cannot be changed once created. This means that any modifications made to a string result in the creation of a new string object rather than modifying the original one.