Without beating much around the bush let me get straight to the point. The UPSC exam is a 3-phase affair:

Phase 1 is the UPSC Preliminary Examination, also called UPSC Prelims. This exam contains questions of the objective type.

Phase 2 is the UPSC Mains Examination, also called UPSC Mains. This exam contains descriptive-type questions.

Phase 3 is the Personal Interview round conducted to test the Personality of the Candidate.

Click here to read about: UPSC Syllabus