What exactly are frequencies

Amplitude, period of oscillation, frequency

Sine curve of a harmonic oscillation

The graphic above shows the sine curve of an undamped harmonic oscillation. This graphic is intended to describe some variables that apply to every oscillation:

• The Deflection \$ y (t) \$ in \$ y \$ direction (also becomes Elongation called) shows the momentary Distance of the body from the resting position. The deflection can be specified in the positive or negative \$ y \$ direction.

• The amplitude is the amount of the maximum deflection in the \$ y \$ direction. In the case of harmonic undamped oscillation, the amplitude is constant, i.e. the distance from the rest position is the same for both reversal points.
• The Oscillation period \$ T \$, indicates how much time the vibrating body needs for a back and forth movement. The unit of the period of oscillation is seconds:

Unit: 1s [second] period of oscillation \$ T \$

frequency

Often the frequency \$ f \$ of an oscillation is specified instead of the oscillation period \$ T \$. The frequency is the reciprocal of the period of oscillation and indicates the number of oscillations that a body has in a certain time \$ t = T \$: