If you filled out a W-4 when you began your internship, you should be receiving a W-2 from the non-profit. Companies are not required to mail W-2s until February 1, 2016. If you do not receive one by mid-February, give the company a call to double check the status.
Whether or not you need to file a return depends on many factors. Low income tax payers are not always required to file but often times students do in order to take advantage of the many Education Credits available. Also, if money was withheld on your W-2, then you'd want to see if you're entitled to a refund.
