Since it is for homework I will not answer but give you a link to articles on these subjects written by actual Hindus. This way you will gain good Karma for yourself by your own hard work.
Good luck with your homework and if you have any further questions fell free to E-mail me.
Karma in sanskrit mean “Action” in english, there are good karma which are virtue in nature and Bad karma which are sinful in nature. When a person execute an action Good or Bad Karmic impressions subtly and unknowingly sowed into one’s consciousness.
Reincarnation or rebirth is when a person dies, based on the karma committed will take into rebirth into another body. Its a transference of consciousness as the current home or body has broken down.
Lastly Caste system is India old tradition in forming different classes of ppl. From Warriors to Priest to Businessman to working class and to the slaves.