RCS is designed as the (eventual) successor to SMS and MMS, but it's a bit of a mess right now. Several carriers have their own implementations of the standard, often incompatible with each other. Google's Jibe RCS Cloud is quickly gaining ground, but there's still only one US carrier supporting it - Sprint. Now Samsung has announced its own RCS cloud.
Samsung is billing its RCS service as a complete package - it includes everything that carriers need to get RCS up and running for their customers. This includes supported devices, Samsung-made messaging apps, and cloud-based RCS servers (similar to Jibe RCS).
Now before you rush down to the comments and type "Samsung is fragmenting RCS," keep in mind that Samsung's service is using the same RCS Universal Profile that Jibe is, and is designed to be intercompatible with other RCS clouds. So presumably once Samsung and Google get everything squared away, users on both platforms could communicate with each other using RCS without a hitch.
Samsung is offering its RCS solution in both full configurations and modules, so carriers can choose what they want. The company says that it is working with Deutsche Telekom, KT, SK Telecom, T-Mobile, and Vodafone at the moment. I assume at least some of these carriers aren't fully switching over, as Deutsche Telekom is already using Jibe Cloud, and T-Mobile and Vodafone are using their own RCS implementations.
Samsung says its RCS service, "will be supported by Samsung smartphones running Android Marshmallow or later." It's not entirely clear what someone on a carrier with Samsung's solution would use, if they don't own a compatible Samsung device. Android Messages currently supports Jibe RCS and Vodafone RCS, so maybe it will be updated to work with Samsung's service as well.
Hopefully we'll know more when we start to see Samsung's RCS service actually live. In the meantime, see the source link below for Samsung's full announcement.
- Samsung Newsroom