According to Google, “Chat features are already available for some of you in Messages, and today we’re starting to broadly roll them out in the U.S. If you already have Messages, you’ll also be prompted to enable chat features in the coming weeks. If you don’t have Messages, you can download it on the Play Store. We expect this service to be broadly available in the U.S. by the end of year.”
For those who are unfamiliar, RCS is essentially the evolution of SMS. The problem with SMS is that it is limited in terms of what it can do, which is why messaging apps like WhatsApp are extremely popular where it allows users to not just send text messages, but they can also send photos, videos, and more.