This is the start of a
method declaration. What it says is "I am declaring a method named
printAL with a single parameter of type String. The method should be treated as public and as static, and it doesn't return a value (that's what
void means)."
So yes, the code is creating that method. It's not part of the standard
Java API because you don't need to declare those things in your code, they are already declared in somebody else's code.
In Head First Java there should be a description of what it means to declare a method; you may have already passed over that and not absorbed it or not noticed it. So look around in the book, maybe look in the index for "method declaration" or some form of those two words.