When you enable your tier structure, affiliates will be recruiting other affiliates in to your affiliate program for you. There are two different linking styles you can enable for them to use.

Forced Linking

This will produce a special link that must be used when recruiting. The affiliates get this very specific link within their affiliate dashboard and its used only for recruiting other affiliates.

Embedded Linking

When using this setting, any affiliate marketing link will work for recruiting to. Meaning, if someone clicks a regular marketing link and winds up joining your affiliate program, the affiliate whose marketing link was clicked will be assigned the tier.

The key differences here would be the actual link itself being used but also the landing page. The forced linking method uses its own dedicated landing page you can define. Usually the main page or signup page of your affiliate program, since that is the activity you want the person clicking the link to do. The embedded linking method just uses the regular marketing links so the landing page(s) for those links are defined in your regular marketing configuration.