When the long hand points to the 12 it is ' o'clock '. When the long hand
points to the 6 it is 'half past'.
This clock says 8 o'clock: the long hand points straight up and the short hand points to 8. This clock shows the time of 8.00
This clock says half past eight: the minute hand has travelled half-way around, and the hour hand has travelled half-way towards the next hour. This clock shows the time of 8.30