SMS (Short Message Service) messages contain text only. One text message can contain 160 characters; when you near the limit, a counter appears. If you type more, your message is sent in a series of SMS messages.
You can send one SMS message to multiple people, and replies are delivered in separate, not group, conversation threads (unless you and your recipients have group messaging enabled).
SMS messages are included in most carriers' text messaging plans and do not use cellular data.
MMS (Multimedia Messaging Service) messages can include unlimited text plus a photo, picture slideshow, video, or sound file.
You can send one MMS message to multiple people using group messaging, containing text only or text and media, and replies are delivered in group conversation threads to each person in the group.
MMS messages use cellular data and require a cellular data plan or pay-per-use payment.
Group messaging lets multiple people carry on a group conversation. All replies from recipients are delivered to all recipients, in a group conversation thread.
Though you send one message to multiple recipients, you are charged for each message received. Group messaging:
If you don’t want to receive replies in group conversations, you can turn off group messaging in the Messages app.
If you’re having messaging issues, try these troubleshooting steps.