For waves with fixed speeds, wavelengths and frequencies are inversely proportional to each other.

To see this, note that speed = wavelength * frequency

Intuitively, wavelength is the length of one wave (the crest to the trough, back to the crest); and frequency is the number of such waves in a second. Clearly, the product gives the speed of the wave.

Consider light - its speed is fixed. Depending on the frequency, the wavelength changes.

wavelength(red light) > wavelength(blue light) because

frequency(red light) < frequency(blue light)

In fact, the relationship is such that

wavelength(red light) * frequency(red light) = wavelength(blue light) * frequency(blue light)

The same goes with sound. Higher frequency sound waves have smaller wavelengths.