This wiring diagram illustrates the situation where the power comes into the light box first, and then on to switch #1, and switch #1 to switch #2.
This requires a 2-wire from the light to the first switch, and a 3-wire between switches.
How is it that the bottom white-wire is part of both a 14/2 and a 14/3 wire?
You use one of the switch boxes as a junction and tie he white wire together with a wire nut… The wire potential is the same, so it “can” be shown this way, but it would be more clear if it showed a junction point with a dot or some other symbol.
this diagam is not correct please remove it!!!!! it is not a 3way switch!
Are you Canadian? This is what the US calls a 3-way. However, it’s not up to the NEC 2011 code. Most of the diagrams here aren’t.
The latest in my series of ‘Internet Electrician’ E-Books covers the use of a digital multi meter.
This is one of those ‘tried and true’ tools of the trade that electricians can’t imagine doing their job without.