Difference between intime and ontime

What is the difference between "in time" and  "on time"?

Intime : Before the fixed time

For example lets check the following sentence: The collector came to our school intime

Ontime: Exactly at fixed time

For example: The collector came to our school ontime.

இரண்டு வோர்ட் சரியானவை. அந்தத்த சூழ்நிலையை பொறுத்தவை.