What is meant by a wave?

Hint: We know that the waves are caused due to disturbances which cause the particles in the medium to move. There are broadly two types of waves namely, the longitudinal and transverse wave. These waves are given by the wave equation and also carry energy.

Complete answer:
The wave equation of a wave is given as $y(x,t)=Asin(kx\pm\omega t+\phi)$ where,$x$ is the position of the wave at time $t$, $t$ is the time taken, $A$ is the amplitude, $k$ is the wavenumber and $\omega$ is the angular frequency of the wave. This is used to describe the motion of the wave.
Generally, one wavelength is the phase difference of $2\pi rad$. From the wave equation, the wave number $k=\dfrac{2\pi}{\lambda}$ and the angular frequency $\omega=\dfrac{2\pi}{T}$ where $T$ is the time period of the wave and can also be written as $T=\dfrac{1}{f}$, $f$ is the frequency of the wave.
The energy of a wave is given as $E=h\nu$ where $h$ is the Planck’s constant and $\nu$ is the frequency of the wave.
Waves are sinusoidal in nature and are generally expressed in terms of sine functions. But they can also be expressed as cosine functions. We know that the angles can be represented in the terms of degrees or radians. Here in wave functions, we generally use radians. Also, we can convert radians to degree and vice versa using $1 \;rad=\dfrac{degree\;\times\pi}{180}$, which is to say that $\pi$ is equivalent to \[{{180}^{\circ }}\].

Note:
A sound wave is both longitudinal and transversal wave which needs a medium to propagate. The propagation of sound is due to rarefaction and compression of the waves. Whereas light waves are transverse waves, which don’t need a medium to propagate.