The document discusses the difference between the phrases "on time" and "in time". "On time" means arriving or occurring at the exact, appointed time. For example, if someone needs to be at school at 8:30 am and they arrive at 8:30 am, they have come "on time". "In time" means arriving a few minutes before the appointed time. For instance, if someone needs to be at school at 8:30 am and they arrive at 8:25 am, they have come "in time". The document provides examples of using each phrase correctly in sentences.