The PMP exam is a computer based exam with 200 multiple choice questions. This means that each question has exactly one correct answer. The exam will give you exactly four hours to answer these questions. If you prepared well, this should be a breeze. Most find four hours to be more than sufficient for the exam. (It took me 3 hours and 58 minutes because I wasn't feeling well on that day.) Out of these 200 questions, 25 questions are pretest questions. These are randomly places through out the exam and are used for research purposes. These questions will not count towards your final score. But even though you will only be evaluated on the basis of 175 questions you still must answer all 200 because you won't know which are the 25 pretest questions.
PMI does not release the actual score that is required for you to pass the exam. All they tell us is that "The passing score for all PMI credential examinations is determined by sound psychometric analysis." So nobody but PMI knows how many questions you have to answer correctly in order to pass.
This is important: Remember that there is no negative marking on the exam. This means that you are not penalized for questions that you answered incorrectly. There is just "correct" or "wrong" for the scoring. This means that if you leave a question unanswered your answer is "wrong". So remember not to leave any question unanswered. You need to answer them all.
After you click on finish and submit the exam, you will see on-screen whether you passed or failed. This takes about 10 seconds but feels like an eternity. You will also receive a printed examination report that tells you how you did in the various process groups.
To feel confident that you can do it, you must have undergone enough preparations and must have taken practice exams several times based on the lessons learned from the study materials of your choice.