This is a worldwide association for studying and apprimoring the techniques of project management. There are units everywhere.
If one want to join it, he must first take some training and then apply for the test. The test is a series of questions to test your knowledge about the standards and techniques described in the "PMBOK", the collection of information regarding project management. The test can be done in a unit in your region. Check it in the internet, a search will reveal it.
The test serves as a certification for you. Some enterprises keep in their personnel some people with the certification. Other people act like consultants, and use the certification to charge customers a little more. After all, this is a collection of rules that are usefull if you're supposed to be a project or program manager.
I had a course myself some time ago, I use it almost everyday, but chose not to spend money and time in the certification due to my work profile. It's up to you.
I did not do the test. I don't think I will, I will not make money with it (at least by now).
The test itself, I have some simulated questions, and it's quite normal multiple choice question type, with some tricks, as all multiple choice questions. Just stay cool and everything is gonna be fine. I had 90% in the training final test, with questions from the certification test itself.
By the way, for the certification, you'll have to show your participation in a minimum amount of work hours in project management I don't remember how much. As a tip, I would say: save your work for future reference...