Every Landing Page is designed with an end goal in mind. A Landing Page Conversion means that a visitor on the Page actually performed the action that you designed the Page for.
A Landing Page Conversion Goal is meant for setting conversion targets for your Landing Pages, i.e., a target number of people who should ideally click through the Landing Page.
Using the Landing Page Conversions Goal type, you can set conversion goals for individual widgets used in the Landing Page.
For example, you can set click targets for your CTA buttons, hyperlinked images, or coupon redemptions.
Suggested Reading: How to set Landing Page Conversion Goals?