Literal values are any hard coded values in C#; that is, any value you use in place of a variable.
Eg:
Code:
string name = "Peter"; //Peter is a literal string value
int age = 5; //5 is a literal integer value
double tuition = 300.0; //300.0 is a double literal value
decimal bonus = 100.0M; //100.0M is a decimal literal value
//etc.
As long as the value is hard coded; that is there is no way that the value can be changed at runtime, then the value is a literal.