Perhaps to explain a bit more in "long hand" if anyone trying get to grips with what all these bits mean....
Frequency: is the number of occurrences of a repeating event for a standard duration of time
Time: The standard SI unit of time is the second.
Period: This is the duration for one cycle of a repeating event.
so a frequency 500Hz is 500 cycles per second.
i.e. If you drew a graph for an ac voltage.. one cycle would:-
start at 0v to a positive peak then back to 0v then to a negative peak then back to 0v!
that is
one duration of the event.. {the period}
if you get 500 of them per second then the duration of that one period is
1/500 =
0.002 of a second.
or working backward if it takes 0.002 of a second for one period...
how many can you cram into 1 second?
1/0.002 = 500cycles per second {Hz}!