The Chunin exams are test for genin to get to the next rank in there job as ninja. When ninja become chunin that get higher ranked missions. To become a Chunin you must take the test. The test has three stages to it. Written test, Survival test, and the The showdown test.
First the Written test is only 10 problems long and they have a set amount of time to finish. They get the first 9 problems. Then when time is up they get the last problem. If they get caught cheating 5 times there out and so is there team. If you at least get one problem right you move on to the next part of the test.
Second is the survival test. They have to get two scrolls. A heaven and a earth scroll. Then get a random scroll so they have three days to get there next scroll and bring it to the middle of the forest. IF one of your team members die your team fails.
The preshowdown test. Only 10 ninja can go on to the last test. So if there are more then 10 they fight until one gives up or gets knocked out.
The showdown test. The ninja have one month to train to learn new skills for the ones who passed the second and preshowdown test. Then this test is just like preshowndown test just in front of more people. Also the leaders of what village the ninja come from can get to become a chunin. So even if you pass the test you might still fail. If you lose your match you still have a shot to become a Chunin. If you kill your enemy you will fail the test and not become a chunin for that years test.