I shall provide a quick summary and hopefully it helps!
Risk Assurance is the audit team that works with processes and controls of a business - i.e. they understand and test automated controls and IT dependent controls, so that the Core (regular) Audit team can rely on their work. The Risk Assurance team have an integral role for the audit, especially in an IB where a lot of processes are automated. They also reduce the workload for the Core Audit team - for example, if the Risk Assurance team confirm an automated control feed between X and Y is working correctly, the Core Team doesn’t need to manually test what comes out of Y, but rather just what is inputted in to X.
Core Assurance is what you have heard about before - general Audit in terms of testing etc.
Both teams interacts with the client regularly and both have busy seasons - albeit at different times (Risk: Sept - December ish, Core: Jan - March ish).
Both roles have the same ACA exams and you all interact and work together through this process! All in the same classes in college and sitting the exams together.
In terms of choice, think about what you want to do next - Risk Assurance is more IT related and so consider if this is something you want to progress into!