An immutable type, in the context of C#, is a type of object whose data cannot be changed after its creation. An immutable type sets the property or state of the object as read only because it cannot be modified after it is assigned during initialization.
Immutable types are designed for efficient memory management and better speed, which makes them suitable for objects with synchronization requirements. Immutability provides better code readability by making changes in program state visibility and isolating the operations that change state from those that do not. Immutable types provides higher security than mutable types.
An immutable type is used where data is to persist after being assigned once, but without any requirement for the data to be changed in the future. Because immutable objects do not change their state, they are more useful in multithread and multiprocess scenarios, as multiple threads may read or write an object, which may cause racing conditions and synchronization issues.