Amplitude is the maximum displacement of points on a wave, which you can think of as the degree or intensity of change. This maximum displacement is measured from the equilibrium position. The following picture shows a diagram of a sine wave. The diagram shows amplitude and wavelength, which is the distance between two successive like points on a wave. Wavelength is like the distance between two adjacent peaks or two adjacent valleys. Stated another way, wavelength is the time required to complete one full cycle of the wave.
The frequency is the number of wave cycles passing a point per unit time. Stated another way, it is the number of oscillations per second in the wave. A higher frequency means a shorter wavelength, and a lower frequency means a longer wavelength.