Example of Rule Types are Classes, Properties, Sections, Data Pages etc. Basically all different types of rules that we get to see from Record Explorer from Dev studio.
Ruleset is a container of rules.
For example, when we create a new property, behind the scene system creates an instance of Rule-Obj-Property. When we save this rule, we need to provide a Ruleset and version so that it can be packaged for deployments/ participate in Rule resolution etc.