Hi Manjeet,
During the sprint reviews all the stories being worked on are demonstrated. When some stories remain incomplete by the end of the sprint , a question to be raised : have those stories been sliced appropriately to be consistent with resources availability. It is not uncommon to spread out one fairly big story across multiple sprints and redefine smaller ones . If a story got incomplete for unexpected and unplanned reason then a decision to be made on that story before the sprint review on moving that story to the next sprint based on its priority in the backlog. Then, during the sprint review you dem up to the point where the work on that story has stopped. Note that reasons why this was completed or discussing associated issues are to be addressed in retrospective where you may need to tune and adapt to upcoming sprints.