The ending can be summed up pretty easily in three words: Happily. Ever. After.
Simba battles and defeats Scar, which means good wins out over evil. Then, Simba and Nala get together and have a cub, ensuring that the royal legacy will continue.
In the movie's final scene, Rafiki, Simba, and Nala appear on Pride Rock, with Rafiki holding up Simba and Nala's son and heir apparent to the throne. This scene is meant to serve as a bookend to the first scene, which is basically identical except Simba is the cub. This parallel imagery underscores the Circle of Life theme, implying that all events continue in a perfectly symmetrical and self-contained cycle.