Actions – known as transactions in SAP. To perform a function, more than one transaction may be required to be performed.
Permissions – authorization object in SAP, which form as part of transactions.
Risk Rule - possible combinations of transactions and permissions for a business risk. More about risk rules and types of rules can be found.
Rule set – categorize and aggregate the rules generated from a risk. When you define a risk, you attribute one or more rule sets to that risk. Similar to business processes.