The Samsung messages app is RCS compatible or capable. Your carrier is also running a RCS network infrastructure.
The messages app scans your contacts and connects to your your carrier database and determines how many of your contacts are using RCS capable phones and their RCS network infrastructure. It marks the contacts with a blue dot if they have met the requirements for sending and receiving messages in chat mode.
You should be able to send and receive multiple large image files at full resolution. Also uncompressed video files and your text messages character count limit should go much higher. When you send mms and text messages to contacts without the blue marker the messages app will send and receive mms and text messages using the standard messaging format.
Edit Oct 5th, 2020
My carrier T-mobile in partnership with Google has implemented RCS Universal Profile. This opens up a lot of new contacts for chat messages with friends who are using Googles jibe network. The original goal was to have Interoperability between all the carriers using Googles jibe network infrastructure. Some carriers signed on right away while others created their own proprietary chat networks. I was originally only able to chat with contacts using the T-mobile chat network but today that has all changed for the better. We still need a few more of the major carriers to join in so we can all use chat messaging regardless of which carrier we're with.
It's for ppl that have Samsung Galaxy phones and or are with the same company u have.. it let's u text n reply n both u can see when the other is writing or seen the text. And it helps send pix and video to each other quicker. But it's really just letn u no they have Samsung Galaxy phones
That's not quite true, there is only one contact on my phone with the dot. My husband and I have the same exact phone, same company and talk on video sometimes but there isn't a dot by his name. I have a few contacts with the same company, with androids, with Samsung and none of them have the dot. This truly is something that needs to be answered by Samsung.
It doesn't mean that they have the same company I do. There are contacts on my list that I know do not use US cellular, which is the company that I use.
What he means, is that the blue. Is next to contacts that do not have the same carrier nor the same phone as myself. I have a blue dot on two contacts one has an iPhone and I have an Android. I have a blue dot next to a contact with Verizon while I have T-Mobile. So what does the blue. Mean can Samsung answer that for us?