difference between frequency and angular frequency?

Question

I am talking about the case in the simple pendulum .

Answer 1

The two terms are similar but refer to slightly different things.

Frequency refers to how often a particular thing repeats, and is measured in cycles per unit time.
i.e. cycles per second.

Anqular velocity refers to how fast something is rotating, and is measures in degrees or radians per unit time i.e. degrees per second.

Answer 2

Frequency is oscillations per second. Angular frequency is how many radians or degrees per second the pendulum is moving at any particular time. For a pendulum, the former is constant, while the latter oscillates sinusoidally (more or less) with time, being zero at the peak and maximum at the bottom of the swing.