Mensa is a society comprised of those who have a high intelligence. In order to get into the society, you have to take, and pass, a test of difficult questions and puzzles. Mensa is typically reserved for those who are in the top 2% of intelligence. There are some questions that you can practice with if you want to see if you have what it takes to pass the test and join an elite group of people.
Most of the questions on the Mensa admission test are multiple choice. They also generally involve some form of pattern matching or other logical deduction. The Mensa test is something that requires you to think outside of the box with some questions, and there are some questions that you have to be able to work out with pencil and paper by knowing math and other subjects!
Most of the distance problems are measured in meters, so if you plan on figuring out the right answer, you need to know the metric system. One type of question that you might see involves two people who leave a location at the same time. One person walks in one direction for three meters, and the other person walks the opposite way, turning after five meters and then turning again. You need to find the distance between the men.
Another often seen question type involves age. You need to figure out how old someone is based on the age of a sibling and how old they were ten years ago. Analysis questions are big on the test, similar to those that you would find on an SAT test. It is not uncommon to see a simple question like: "pear is to apple as potato is to what?"
While taking the test, you will see questions about what one person likes. Peter will like Susan and not Shawna, William but not Charles. You need to figure out the logic in the names to determine who he will like out of two names that are given. There are pictures to look at in puzzles, and you will see words that have a common word at the beginning to create new words.
All Mensa question topics are culturally fair, which means you're not going to see any questions pertaining to politics, religion, or specific institutions that might exists in some countries but not others.
For a better idea of the type of questions on the Mensa test, take our quick 6 minute practice test or our full 12 minute practice test. Taking either of those tests a couple of times should get you up to speed on the possible questions you might encounter, but for a much more thorough overview of the type of questions you might encounter, we highly recommend you go a step beyond online tests, and purchase a well written preparation book such as the Genius Tests Practice Test Guide.