In this project, we compared how experts and lay users understand algorithmic systems. To specify the knowledge gaps, we conducted an expert focus group (N = 3) and semi-structured in-depth interviews with experts (N = 10) and lay users (N = 11), including a drawing task. Reflexive thematic analysis of our material revealed group-specific and common themes: Experts understood algorithms as a decision-making process and were aware of the context-dependency of algorithms. Lay users, in turn, understood algorithms as intelligence and as data structuring. They focused on the tangible and visible elements of algorithmic systems. Both groups also understood algorithms as a sequence of actions. The different understandings might be driven by group-specific experiences and purposes to use algorithmic systems. Based on our results, we argue that user-informed explanations could consider the context-dependency of algorithmic systems and highlight their limitations.
