Maintaining quality over time and ensuring as long a period of proper functioning as possible are precisely the objectives of the reliability concept. Reliability is nothing but a quality characteristic of long-term use products which describes their capacity to remain in proper working order. Of course, there are no products that can remain in proper working order ad infinitum and under any operating conditions. It is for this reason that reliability describes the capability of products to work properly over a given time and under certain operating conditions. In practical terms, there is no organization out there that doesn't need to carry out specific maintenance activities. The successful implementation of the above and the outstanding performance of a company are conditioned by the familiarization with and mastering of these theoretical aspects of reliability and maintainability, as well as the ability to apply these. The work at hand is intended for students and / or specialists in the manufacturing or services domain. In a broader context, it is in fact of use to all manufacturers and beneficiaries of long-term use products.