If you have a matched source /line / termination a pulse waveform will be identical at both the transmitting and receiving ends. If the source/line/termination are not matched some of the power in the pulse will be reflected, causing pre-shoots and over shoots (pigs ears) on the pulse edges. For any given length of line these will be worse the sharper the rise and fall times of the pulse is.
Functionaltiy wise, they can often be seen on TV pictures, the added waveforms will give an echo effect and the left hand edge of bright object will be seen to have a black or white edge. They also cause digital communications to become unreliable, as a pre-shoot can be detected as an added digit.
Frank