What is the difference between in, on, and at?
You can look this up online. This question has been answered literally thousands of times before, and is dealt with in every proper English textbook.
Search using these keywords: <em>difference in on at</em>
After researching, tell us what you understand. :)
Also Lucy, regarding the prepositions IN, ON, or AT, see as follows:
http://www.englishgrammarexpress.com/grammar/in-on-at-time
https://www.englishclub.com/grammar/prepositions-at-in-on-time.htm
https://www.wisc-online.com/learn/humanities/linguistics/esl2103/prepositions--in--on--and-at
I'm im my bed, on my pillow, at my place. What's yours?
I agree with Michael, but prefer u to memorize them by using in application ...