it sounds to me like you are being asked to do a care plan on a specific community. in this case, the community would be your patient. a community diagnosis would be your nursing diagnosis(es) for the community you have chosen based upon the problem(s) you determine it has. objectives would be your nursing goals and outcomes. limitations would be restrictions that will affect achieving maximum goals; these would be underlying problems (in a patient this might be an underlying chronic disease) that you cannot do anything about but have to make allowances for. (for example: if you have a stroke patient who has a right sided paralysis the patient's goals that he can achieve are going to be limited by the paralysis he has.) a community might be restricted by economics, education, ethnics, social networks, culture, politics and any other number of things. your rationales, as always, are the logical reasons (why) your interventions are going to work.
since you are assigned the introduction part of this assignment, i would think that your part in this would coincide with the first step of the care planning process. that is, assessment and data collection. for a patient, this would include a review of systems and physical assessment. for a community, it would include going through a history of the community and then doing a physical walk through to evaluate it.
do you know specifically what you are to be assessing for in the community you have been assigned? usually, for these projects, it is the health resources available to the residents who live there. this includes all things that affect a person's health: garbage collection, water purification, sewage, air pollution, availability of health care (hospitals, clinics), police protection, etc. i would look at maslow's hierarchy of needs to make sure you are including all human health needs. if you have a textbook on community nursing these things should be listed in it. otherwise, you will need to go to a library and do some research on what a healthy community should ideally be. use that as a perfect template for your assessment of the community you have chosen. when you make your assessment of your chosen community, the things your chosen community doesn't have when compared to your perfect template will then be your abnormal assessment items that you will develop into nursing diagnoses for the community, develop goals for and interventions. the problem you are going to have (the same one we had when we had when we did this when i was a senior) is that there really are no nursing care plans out there for you to look at on this. you have to figure this out on your own. so, your part, the introduction, will be to explain what the perfect community should be and how your chosen community for this project matches up to that. the other people in your group should have the responsibility of determining the problems (community diagnoses, limitations), objectives (goals) and interventions (with rationales).
the steps of the nursing process (written care plan)
assessment (collect data)
nursing diagnosis (group your assessment data, shop and match your abnormal assessment data to likely nursing diagnoses, decide on the nursing diagnosis to use)
planning (write measurable goals/outcomes and nursing interventions)
implementation (initiate the care plan)
evaluation (determine if goals/outcomes have been met)
you should check out the nursing student assistance forum on allnurses for help with student assignments (http://allnurses.com/forums/f205/
welcome to allnurses!