Periscope is a free broadcasting app owned by Twitter that allows users to livestream videos from around the world. You can search the app for live broadcasts and user profiles, but you can't locate archived videos of past streams over 24 hours old. You can view some completed live streams by tapping the TV icon located on the bottom toolbar. This will give you a list of live streams that ended in the past 24 hours from users you follow. You can also view older live streams if you have a direct link to a saved web replay or if a user uploads the video to another service, such as YouTube.