These days there are people who insist on broadcasting their whole live for the world to see, with plenty of services willing to make it happen. Today Instagram is taking it a step further, letting guests join in on your live broadcasts.
Live video was first introduced back in November, with a number of extra features added in the months since. Instagram is now testing the guest feature with a select number of users, after some improvements it'll start rolling it out to other users in the coming months.
It's all pretty simple. One person does the broadcasting, and can bring in guests that'll start broadcasting alongside them (see above). Meanwhile friends and followers will like the stream and comment on what's happening as it happens. Guests aren't permanent, and can be removed at any time - letting you stream with someone else instead.
So that's basically it. Go and have fun with it, if that's your thing.