"The European Council shall provide the Union with the necessary impetus for its development and shall define the general political guidelines thereof."--Article 4 of the Treaty on European Union
"The European Council brings together the heads of state or government of the European Union and the president of the Commission. It defines the general political guidelines of the European Union."-- European Council web page
The European Council (not to be confused with the Council of the European Union!) meets at least twice yearly (in practice, four times yearly, and sometimes more), usually in Brussels. Council meetings shape the direction of all EU activities and result in Presidency conclusions, published after each meeting.
Europa's European Council page : This official page provides an excellent overview of the activities of the European Council.
Definition of European Council (from the EUROPA glossary)