Every SHM is fully described by three parameters: amplitude $A$, angular frequency $\omega$, and initial phase $\phi$. The displacement equation $x = A\sin(\omega t + \phi)$ contains all information. From it, velocity $v = dx/dt = A\omega\cos(\omega t + \phi)$ and acceleration $a = d^2x/dt^2 = -A\omega^2\sin(\omega t + \phi)$. The defining condition is $a = -\omega^2 x$, meaning acceleration is always directed toward the mean position and proportional to displacement. Any system satisfying this condition executes SHM, regardless of whether the restoring force comes from a spring, gravity, or any other source.