language agnostic - What's the difference between an argument and a parameter?

When verbally talking about methods, I'm never sure whether to use the word argument or parameter or something else. Either way the other people know what I mean, but what's correct, and what's the history of the terms?

I'm a C# programmer, but I also wonder whether people use different terms in different languages.

For the record I'm self-taught without a background in Computer Science. (Please don't tell me to read Code Complete because I'm asking this for the benefit of other people who don't already have a copy of Steve McConnell's marvellous book.)

Summary

The general consensus seems to be that it's OK to use these terms interchangeably in a team environment. Except perhaps when you're defining the precise terminology; then you can also use "formal argument/parameter" and "actual argument/parameter" to disambiguate.

Answer

A parameter is a variable in a method definition. When a method is called, the arguments are the data you pass into the method's parameters.

public void MyMethod(string myParam) { }

...

string myArg1 = "this is my argument";
myClass.MyMethod(myArg1);