Hi, I don't know where you are from but in my country Bangladesh, a study plan involves giving a page long explanation about:
a) the reason you want to study in Canada
b) your overall educational goal
c) why you are not pursuing a similar degree in your country of residence
d) your ties to your home country( that is what are the ties that will ensure that you will come back once you are done studying)
e) how this opportunity will enhance educational opportunities in your home country
e) a cv should be attached to this plan if you've been out of university for the last two years
f) if you are a minor, explain why do you want to go to school in Canada? What is the immigration status of your parent/guardian or something along those lines.
Your purpose of visit needs to be solid and you should have some sort of proof that will convince the visa officer that you will come back after getting your degree.
Some people write this plan in the form of a letter addressed to a visa officer.
Hope this helps.