The purpose of failure analysis is entirely positive: to prevent further failures. Failures occur when some system or part of a system fails to perform up to the expectations for which it was created.
A car transmission fails
A pipeline leaks
A cell phone explodes
The concept of failure is easy to understand intuitively. But underneath that intuitive understanding are important conceptual principles which are commonly either misunderstood or not considered at all. Failure itself is a human concept. Materials do not fail in and of themselves. They follow the laws of nature perfectly. If a part is loaded beyond its tensile strength, it breaks. Until that stress level is reached, it does not break. When a part fails in service, it was under-designed or poorly manufactured for the circumstances in which it was used. (reference)
Case examples: