void (C# Reference)
When used as the return type for a method, void specifies that the method does not return a value.
void is not allowed in the parameter list of a method. A method that takes no parameters and returns no value is declared as follows:
void is also used in an unsafe context to declare a pointer to an unknown type. For more information, see Pointer types (C# Programming Guide).
void is an alias for the .NET Framework System.Void type.
C# Language Specification
For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.