LED_StatusOfButton example help

I just used this to get my project up and running but I have a couple questions on why I did certain things.
// If state has changed…
if (isPressed != btnState) {
if (isPressed) {
} else {
btnState = isPressed;
im having trouble finding the on/off commands and wonder where they came from and how thy work. is there a reference for this?
Also in the code it has
timer.setInterval(500L, buttonLedWidget);
what is the L for?
thanks just want to have a better understanding.
And the code worked great so thanks for the example.

It means that number is LONG and not other type. As by default INT assumed.

THX again. the link was good I had trouble finding it before.