Rich Communication Services or RCS is a communication protocol between mobile telephone carriers and between phone and carrier, aiming at replacing SMS messages with a text-message system  that is richer, and can transmit in-call multimedia.

The RCS protocol is much more useful than SMS. Added abilities are…

• chat with content sharing, driven from an RCS enhanced address book,
• enhancing the messaging and enabling sharing of files,
• 1-2-1 Chat,
• Group Chat,
• file sharing,
• content sharing,
• Social Presence Information,
• IP Voice call,
• IP Video call,
• Geolocation,
• Visual Voice Mail,
• Support for Chatbots,
• Support for vCard 4.0

It looks like all of the major carriers now support RCS.

Applications that support RCS are Google Messages, Facebook Messenger, WhatsApp. iMessage does not support RCS yet.