In this slide, some of the effects that transmission lines have on the waves propagating through them are displayed.
The waveform on the left is the input voltage applied to one end of the transmission line.
The other waveform is the voltage obtained at the other end, which is left open-circuited.
There is a delay between the two waveforms - this delay is proportional to the length of the line.
Also, overshoot and reflections manifest themselves in the output waveform.
It is important to be able to simulate these effects in order to assess a digital circuit's performance.