I'm a newbie and just got started with Arduino. I have been playing around with the book Getting Started With Arduino and felt so interesting. Though I got stumbled upon an example from that book. The circuit for the particular example is shown below.
I built this circuit and it worked perfect. Though, I was curious to know what does that resistor and the wire to ground do. So I tried removing them both and I found the circuit is working fine without those two. One behavior I observed is that, I can lit the LED by touching pin 7 with my finger, if those are not present. Can someone explain me why this is all about?
Thanks in Advance.