It is actually the equivalent of a private backing field that is marked readonly. public class Person{ private readonly string name; public Pers

It is actually the equivalent of a private backing field that is marked readonly. public class Person{ private readonly string name; public Person(string name){ this.name = name; } } It's syntactical sugar that shaves a few lines of code off, particularly if you aren't setting values from parameters in the constructor and just want readonly values that are inherent to the class.