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Imagine a circle (in fact a water droplet).  When the light ray hits it from the left, it gets transmitted (refracted).  It goes inside it hitting the outer surface and gets totally internally reflected.  Finally, it gets refracted again from the first surface and reaches observer's eyes.  Observer sees rainbow.

Not all the rays follow this process.  Total internal reflection can take place twice or more than twice.  If  total internal reflection takes twice, the rainbow seen by the observer is called secondary rainbow.  More total internal reflections can take place causing more rainbows however, one seldom sees them as the energy get further reduced.

In some cases electrons are not localised to a particular bond but revolve around a larger space. This concept is called resonance. The following diagrams illustrate this point.

Benzene:

Ethanoate Ion:

Phenoxide Ion: