I just took the pathfinder assessment and it concluded that I would be a good fit for assurance but what actually is it?

Assurance at EY can commonly encompass audit services, financial accounting advisory services and forensics. There is also another sub-service line under Assurance called Climate Change and Sustainability Services which may be of interest too. As a starting point, I would recommend looking into each of these and which industry you are keen to get involved with given that the pathfinder assessment is hinting that assurance would be a good fit for you.