writing program in wdk

Hi
iam new to Documentum i have wrote helloworld component.my doubt is iam using

and in java class

public void changeText(Text txtName)
public void onPress(Button btClick, ArgumentList args)

iam using the above methods
as these are userdefined methods how we know that only these parameters have to be passed as inputs.is anywhere written that for TextField we have to pass Text as input and for Button we have to pass the Buttoion and the argument list like that. and one more thing is i read that Argument list is to encapsulate the arguments and to send those to the server.Please tell me how does it work