It used to be that we could only send messages to other mobile users through SMS, but then applications like iMessage, BBM, WhatsApp, and so on came along that gave us alternatives, better alternatives in fact, because it allowed us to send rich messages that contain videos, photos, and so on.
In an attempt to standardize it, the RCS standard was created that would allow users, regardless of platform, to send each other rich text messages without having to resort to third-party apps, and now it looks like Google has announced that they will be enabling the feature by default on Google Messages.
For context, prior to this announcement, RCS was not enabled by default for Google Messages. Google certainly did try to encourage users to turn it on, but it was entirely up to users whether they wanted to or not. Now with this update, it will be enabled by default, but users will still have the option to opt out if they don’t want to use it.
Google also announced that all RCS messages sent will be end-to-end encrypted, so if you’re still sending SMS, it might be a good idea to enable RCS on Google Messages so that your conversations are more secure and remain private in the event that someone tries to intercept them.
Source: Google Support