It is owned by Twitter, and can be used to create a live broadcast. I have seen it pop-up (pardon the pun) quite a bit this summer, between educators whom I follow periscoping (yes it's now a verb) sessions at conferences, to a favorite band, for King & Country, giving fans a backstage, sneak peek into its summer tour.
Want to know more? Watch this brief YouTube by Sunny Lenarduzzi with instructions on how to use Periscope. She also compares it to Meerkat, a similar app.
I have really enjoyed being a watcher of Periscope. This week, I will be joining the faculty at Cue Rock Star Teacher Camp in Crescent City. I will try to Periscope from there, to try it out! Hope to share Periscope with you soon!