When something supersedes, it takes the place of something else. The 5th edition of your history textbook supersedes the 4th edition.
Most words that include super have something good going on. Supersede is from the 16th-century Latin for "sit on top," and it often means to replace with something better. A version 10 of a computer game will supersede, version 9, making it more exciting. Unfortunately, a person might be replaced too, as in "the younger running back will supersede the veteran player as he gets older." To supersede is generally a good thing, but being superseded is not always that great for the replaced person.