It works exactly like the imessage on ios or the google messages app rcs chat.
This is what Samsung chat messages is all about, you don’t need to use your cellular network on this, but rather a Wi-Fi or mobile data and you’re good to go. Previously samsung users will only have to download the google messages app to enjoy the rcs feature on android, but right now there’s no need to use the Google messages app as you can enjoy rcs chat feature right on your samsung messages app. Samsung chat message is an rcs feature which allows a user to send and receive a text message through Wi-Fi or mobile data, share high quality pictures and videos through the chat feature.
5 Why does my phone say chat message instead of text message? What is samsung chat message?