Try to scan the Bitcoin whitepaper it will help you to get ideas or additional information. Making an essay is a little bit difficult but if you're fluent in english then it would be easy just expand your opinions on you can compose your own words about bitcoin. Try also to search some articles about bitcoin and also the whole cryptocurrency.
I think the main purpose of creating bitcoin is like that, satoshi nakamoto wants to create a digital currency that cannot be controlled by others, so only those who have bitcoin can control it and can be used as the safest and fastest transaction solution.