Use the Full Widget when you want to load a full referral program widget in a section of your website with tabs for handling Registration & Log-in form, Referrals Tools, Program Overview, Statistics and Bonuses.
Use POS when you need to load just the Referrals Tools on specific places on your website like the purchase confirmation page, the sign up confirmation page, etc.
Use Share Links when you want to display just the share link icons in a small section on your website.
Use Referral Tracking for capturing new referrals. It works like a lead landing page, where your leads are the referrals.