Only the person who started a group can add new members (members can leave at any time).
You can also make a Broadcast, which sends the same message to a particular group of people all at once.
And if you get sucked into a boring, high-volume chat, you can’t leave.
How you sign up: Just switch it on in your i Phone’s settings app and enter your Apple ID. In i OS 8, non-cellular devices will also sync SMS messages.
How it handles text: Just like sending SMS messages, although without limits on length.
How it handles photos: i Message lets you send pictures from the built-in sharing sheet, sending them via i Message direct from many apps.
It fails to save incoming photos in your Camera Roll, though, which seems absurd. Once you start a conversation with a group, you can’t remove or add anybody.
Nobody hangs out with a friend for an afternoon and then makes a long speech to summarize their thoughts for the day. We point at things and say, “Hey, look at that.” We deal in snippets.