shift register??

hello.. i have the arduino duemilanove which has 14 digital i/o pins and 6 analog input pins as you all very well know. however, i've seen youtube videos and other stuff that suggests you can control many more than 14 output pins by using something called a shift register. Could anyone shed some light on this topic for me???


It works by using a serial in / paralle out shift register.

You can read a tutorial here: