An hour is a unit of time that is equal to 60 minutes. It is used in both the customary and metric systems of measurement.
If you wake up everyday at 7:00 AM and you leave your house at 8:00 AM, 1 hour has gone by.
24 hours is equal to 1 day.
Hour can also mean a set of appointed time.
Maria's lunch hour with Alfredo is at 1:00 PM.
The train will leave the station at 2100 hours (Military time).