Question

you want to describe the harmonic motion of a swing. you find out that it takes 2 seconds for the swing to complete one cycle. what is the swings period and frequency?

Answer 1

If it takes the swing 2 seconds to complete one cycle, then
that's the period of its motion ... 2 seconds.

The frequency is the reciprocal of the period ... 1/2 Hz.
('Hz' means 'per second'.)