Aptitude tests are standardized tests that are frequently used by companies in order to assess capabilities of job applicants on various topics. Such topics include numerical reasoning, abstract reasoning and verbal reasoning among others. Generally, companies make use of assessment agencies to provide these tests. For example, PiCompany takes care of tests for Rabobank and ABN AMRO, HR Organizer takes care of tests for CapGemini and Ordina, and CEB / Gartner take care of tests for KPMG and PwC. The following link provides a full overview of which tests are used by which companies:
Generally, you are allowed to first see your test results before deciding whether you want them to be sent to your company of interest. However, keeping your test results discrete will obviously not work in your favour of getting hired. Usually, when having applied for a position, your company of interest will send you a link through which you can prepare for the aptitude test. The usefulness of this practice material may differ per company.
If you would like to get an idea of what aptitude tests look like, you could try the free practice tests in the links below. The practice tests are limited, but may provide a decent start.
As mentioned earlier, before making the aptitude test, it is advised to practice. For a fee, you can also practice at various assessment agencies in order to prepare you for the actual test. Before actually purchasing a subscription to practice these tests, it is important to first figure out which assessment agency your company of interest works with, and to figure out which topics will be covered in your aptitude test.