Question

what is the difference between on time and in time

Answer 1

on time means exactly on the given time and in time means within the limit of time.

Answer 2

"on time" - there is an expected time.
 example - We are meeting friends for dinner at 7. I hope we will be on time and we don't make them wait for us.
"in time" - there is a deadline.
 example - If we are past this deadline, we will miss the chance to do something. The show starts at 8 p.m. and no one is admitted after the show starts. I hope we will make it to the theater in time.