If you are a citizen of a EU, EEA (European Economic Area) or EFTA (European Free Trade Association) country, you do not need a visa to get to Poland. However, if your stay in Poland will be longer than 3 months, you will have to apply for a temporary residence permit.
Find out more at:
http://www.malopolska.uw.gov.pl/default.aspx?page=TEMPORARY_STAY_PERMIT
Those students who are not EU citizens will have to apply for a National Visa (D type) to enter, reside and study in Poland. Remember that a visa must be obtained before you come to Poland. National Visas are issued by diplomatic mission or consular offices of Poland abroad.
More information at:
http://www.msz.gov.pl/en/travel_to_poland/visa/