Can one arduino grab a variable (a counter value) from another arduino?

I have one arduino controlling a bunch of LEDs and a button, and another arduino that is controlling a wave shield. I need the wave shield arduino to access the button counter from the first one and switch between "modes" with the lights. How do I do this? I was going to use the rx and tx thing.. I'm not sure.

You need to communicate your count value from one Arduino to another. The most common method of doing so is 'the rx and tx thing', or otherwise referred to as the Serial port.

I2C is also an interesting option to use. Read - http://www.arduino.cc/en/Reference/Wire - and - http://www.arduino.cc/en/Tutorial/MasterReader -

Well how do I use the rx tx thing? I can't figure it out.

PaulS posts code regularly to allow simple and secure transfers via serial.