This category contains free subscription plans, users won't have to pay to subscribe for these plans.
This is one kind of free subscription plan. When users subscribe for this subscription plan, they will become active subscriber of this plan for lifetime. If you decide to use this kind of plan, you should only give subscribers of this plan to access to basic/free resources on your site
This is another type of free subscription plan. Sometime, you want to give subscribers free trial duration so that they can try to access to restricted resources on your site before deciding to become paid subscribers (with higher access level and can access to more restricted resources...). You should set Enable renewal parameter of the plan to Yes so that when subscription expired, they must pay for a paid subscription to continue accessing to restricted resources on your site (or their subscription will be expired and they will no longer be able to access to these resources anymore)