naruto shipuuden/shipunden(or how it is written) is about naruto and his friends when they get older
well in Naruto, naruto is just a little 12 year old and it's mostly about him and his friends and he trains and goes on missions and then there's the chunin exams and sasuke leaving and all those fillers.
in Naruto Shippuden, naruto left the village to train with jiraiya for 3 years and now he's 16. and everyone has gotten stronger. and now its all about naruto trying to bring sasuke back and he has to go on missions and has to deal with the akatsuki because theyre trying to take his kyubi and sasuke is going around and killing all these important people like orochimaru and itachi and deidara and danzo and sasuke is trying to kill naruto and konohagakure. and many people die! even the good guys like jiraiya and asuma!