Students see your LifterLMS catalog, course and lesson pages in the same design as the rest of the community. They enrol, work through lessons and, if you use memberships, see only what their level grants. LifterLMS still decides who can open what; the addon changes how it looks.
Around the courses sits the community. With BuddyNext, each student has a profile, a feed, spaces and notifications. A space per course lets them talk between lessons, and messages run through WPMediaVerse. They no longer leave your site to ask a question in someone else's group.
Because LifterLMS data does not move, current students keep their progress. You can switch the styling on in a staging site first, then make the same change on the live site once you are happy.