Adapted from Wikimedia. Translated and edited by myself.
The red curvy line is a representation of wave.
All the other components are noted down.
The period of the wave (wave period) is usually denoted as the symbol T.
The wavelength is usually denoted with the greek letter lambda (λ).
The frequency of a wave is given by the formula:
Where the symbol f is the frequency.
*Note that frequency is the reciprocal of the wave period.*
The unit for frequency is Hertz. (Hz)
In short, the shorter the wavelength means higher frequency (more waves in a second) and if the wavelength is longer, it means it has less waves in a second.
For musicians,they see frequency as pitch. Everytime when they play a tone, it reprisents a note with a specific frequency. For example:
Start with the middle C in piano, and it goes C, D, E, F, G, A, B, C. This is called an octave. As you press the keys starting from the middle C to the next adjacent keys, you are actually listening to the a note with a higher frequency each time you press it.
So, each time you press the adjacent keys, all you hear is the note with a higher pitch.
Click here for a more details about waves. (high school level)