Transmission Line Parameters
If we consider an infinite lossless transmission line, we can determine the inductance L and  capacitance C per unit length from geometric field considerations.  The three physical  embodiments that are of interest are the two-wire transmission line, the coaxial transmission and  the microstrip transmission line (a simple parallel-plate approximation).

Transmission Line Discontinuities and Load Impedances
If the wave on a transmission line of characteristic impedance Zo arrives at a boundary with  different Zo, or at a discontinuity, lumped load or termination of Z ?   Zo, the single wave moving  in the +z direction cannot simultaneously satisfy the boundary conditions relating V(z) to I(z) on both sides of the boundary.  On one side of the boundary V(z)/I(z) = V+/I+ = Zo and on the  other side V(z)/I(z) = (V++V-)/(I+-I-) = ZL.

Visualization of Standing Waves
The following set of graphs show the development of the reflected wave, beginning with an  initially advancing incident wave moving to the reader's right, which is just about to reach the  load point of reflection.  For these graphs, Zo=50?  and ZL=100? .
I
n the next graph, the incident wave has reached the point of reflection, and the reflected wave  can be seen to be moving back to the reader's left.  In this picture, the waveforms add to a greater magnitude.