The electromagnetic spectrum is a full range of electromagnetic radiation and it includes the frequency and wavelength.  Scientists use this for medical imaging and studying the universe.

Amplitude measures the height of the wave, and it is measured from the middle line to the top of the crest or the bottom of the trough. 

Frequency is the rate at which something repeats over time. There can be high frequency and low frequency. 

Wavelength is the distance between crest to crest. Infrared, microwaves, and radio