Constructors (C# Programming Guide)
Whenever a class or struct is created, its constructor is called. A class or struct may have multiple constructors that take different arguments. Constructors enable the programmer to set default values, limit instantiation, and write code that is flexible and easy to read.
If you do not provide a constructor for your object, C# will create one by default that instantiates the object and sets member variables to the default values as listed in Default Values Table (C# Reference). Static classes and structs can also have constructors.