This is the post / page where you want your visitors to go. Typical examples of goal pages are sign-up pages, sales pages,…
Each visitor navigation from the original page directly to this goal page counts as a conversion (see how conversions work). When doing an A/B or multivariate testing you’ll be aiming at increasing the percentage of users visiting this goal page.
See also the difference between direct and indirect goals.
Posted in: Experiment creation What is the goal page/post of an experiment?