What are the differences between System.String and System.Text.StringBuilder classes?

System.String:

Immutable: Once created, the value cannot be changed.
Performance: Creating a new string for every modification can be slower for frequent changes.
Usage: Suitable for scenarios with infrequent or few string modifications.
System.Text.StringBuilder:

Mutable: Can be modified without creating a new instance.
Performance: More efficient for frequent or extensive string modifications.
Usage: Ideal for scenarios requiring many changes to a string’s value.
Key Difference: System.String is immutable and less efficient for frequent changes, while System.Text.StringBuilder is mutable and optimized for performance with multiple modifications.