Quality assurance is broad discipline, varying in plenty of aspects - internal and external QA teams, black box vs white box testing, manual versus automation testing, feedback versus data driven development, various use of pipelines, workflows and test cases.
Identifying issues in pipelines, procedures, management style, in-game mechanics, integration of features, coherence and fidelity of design/ mechanics, dynamics, aesthetics - all of this is something that can be potentially faulty and/or improved. Proactive approach to team leadership, proficiency in problem-solving and ensuring the clear communication flow, adapting and integrating new processes to the workflows and methodologies, all of these aspects can form the role of someone assuring the quality of end product.
Thanks to my current position I've learned this and many more, and the whole package helped me to understand what can be expected from the role, how helpful can my department and I be in contribution towards the desired final product.
Last thing that I've also discovered is my talent for breaking things that seems to be functional, breaking game boundaries, exploiting in game economics and cheesing in game mechanics to bypass the original design, which helped immensely to me in falling in love with the discipline.
Specific software knowledge
Generic part