Stationary waves and resonance help

I would like to understand the relationship between stationary waves and resonance, what have they to do with each other?

Take a stretched string (e.g. a guitar string) as an example. There are various patterns (modes) of standing waves that can occur - e.g. see diagrams in 1st link. Each of these modes has a specific frequency at which it occurs.

If you externally apply a signal (e .g. sound waves from a loudspeaker, or a vibrator attached to one end of the string) you will make the string vibrate. Resonances occur when the frequencies of the external signal are the same as the standing waves frequencies. This is because it is 'easier' for the string to pick up energy, and vibrate with increasing amplitude, in one of its modes, rather than at frequencies which don't match the modes.

So each resonant frequency is the same as a standing wave frequency.

See 2nd link.