Conformance checking refers to the analysis of the relation between the intended behaviour of a process as described in a process model and event logs that have been recorded during the execution of the process. In this context, a process refers to the coordinated execution of a set of activities to reach a specific goal or outcome.
The activities and their coordination are captured by a process model and data about how the process is actually executed is available in the form of event logs. Combining this results in the main question of conformance checking: how does the modelled behaviour of a process relate to recorded behaviour of a process?