The parameters are the data you pass to a method when calling it. As other languages, C# has different kind of them. An example of a int and a string passed to a method is shown here:
public void SomeMethod ( int a, string b ) { ... }In fact, any field/variable can be passed as parameter ( struct, array, instance class ... ). In th example above, the method SomeMethod will be able to work with the values passed when it is called, a int and a string variables.