Interfacing two arduino boards(noob)

So I'm a noob and I have multiple arduino boards I need to connect to one another... Mostly because I do not have enough pwm pins to run all the required cycles. Basically I have 6 different pulse cycles on one board which function as parents of sort. When one goes off I need its 3 children to light up on a different board. Basically I just need some help on the basic language which will allow the parent board to signal the child board to light up the leds. Thanks