What does string immutability mean and why is this characteristic important for this data type?

Immutability of a string means that once a string object is created, it cannot be changed. Any operations that seem to modify the string actually create a new object. This is important because:

• It ensures thread safety without additional locks.
• It allows efficient use of strings as keys in dictionaries and other collections.
• It simplifies memory management and string caching.

Example in Python:

s = "hello"
s2 = s.upper()  # creates a new string "HELLO", s remains "hello"