"Plans" is where you find access to the plans, and the groups, lessons, and study content under a plan.
A "Plan" is like a private course you can populate with courses, groups, lessons, study content, and individual study items. Plans are created or populated via "Add to plan" links found on many pages.
The "Plans" page lists the plans stored in JTLanguage. You can navigate to plans here, and do other options under the "Actions" column.
The "Languages" drop-down menu lets you filter the plans display to just those for the given language, including place-holders for the languages stored in your profile.