Short Message Service (SMS) & Text Messaging (Texting) are the same thing. It is a means of sending short messages to and from mobile phones. Most SMS messages are mobile-to-mobile text messages, though the standard supports other types of broadcast messaging as well.

Why are my texts sending as SMS?

This could be caused if there is no Internet connection. If the option to “Send as SMS” is turned off, the iMessage will not be delivered until the device is back online. You can force an undelivered iMessage to be sent as a regular text message regardless of the “Send as SMS” setting.

Why are my messages not delivering?

Invalid Numbers This is the most common reason that text message delivery can fail. If a text message is sent to an invalid number, it wont be delivered – similar to entering an incorrect email address, you will get a response from your phone carrier informing you that the entered number was invalid.