It covers the various techniques and design issues that ensure signals are undistorted and do not cause problems to themselves, to other components in the system, or to other systems nearby. An electrical current in a loop generates a magnetic field. The voltage on a line creates an electric field. The impedance of free space is 377 ohms. If I have a perfectly matched antenna, it can be thought of as a transformer that matches the impedance of a line to the impedance of space.
Wires go in, and radio waves come out.
Energy launched from the driver will travel down to the end of the line, reflect and bounce back to the driver. At the driver, it will again be reflected and bounce back to the receiver. This process goes on until all of the energy is lost in heat, or lost through radiation into space. If you place two lines near each other, they will couple to one another either magnetically, electrically, or both. This is because their electric and magnetic fields overlap in the near field and affect each other.