The broad introduction of automated driving promises improvements in terms of passenger comfort and road safety. Since automated vehicles have to operate under a wide variety of conditions, the safety assurance and validation of these systems is significantly more complex than for driver assistance systems. A scenario-based approach using a scenario database for relevant scenarios has established itself to overcome this challenge. The appropriate selection of scenarios is still an important research aspect in this field. There is a common understanding that so called edge cases and corner cases play an important role, but a lot of different understandings and definitions for these exist. Within this paper we review, analyze and discuss the usages and definitions of the terms edge case and corner case in the literature to move into the direction of harmonization.