Incident - an unplanned interruption to an IT service or reduction in the quality of an IT service.

Event - a change of state that has significance for the management of an IT service or other configuration item (CI).
Configuration item - any component that needs to be managed in order to deliver an IT Service.
Component - a general term that is used to mean one part of something more complex.

Problem - a cause of one or more incidents.
Problem management - the process responsible for managing the lifecycle of the underlying causes of one or more incidents.