Chat features is the label Google Messages used for RCS in its settings; turning it on enables typing indicators, read receipts, high-resolution media and Wi-Fi messaging over RCS.
What the switch actually does
Google Messages never called the protocol RCS in the phone's settings. The switch was named "Chat features", and newer versions of the app call the same setting "RCS chats". Enabling it registers the phone number with Google's Jibe backend, which is what lets the handset receive rich messages instead of SMS. When the setting is off, or the phone has no data connection, conversations silently fall back to SMS and MMS.
Why it matters to a business sender
A recipient with chat features off cannot receive an RCS message, whatever the sender does. That is one of the reasons a capability check runs before every send and the message drops to SMS when the handset is not RCS-capable. Most Android phones sold in the US ship with the setting on, and iPhones gained RCS in iOS 18.1, so the share of unreachable handsets keeps shrinking; the support tracker keeps the carrier and device picture current.
On SimplyRCS
The free sender ID test sends a real RCS message to your own phone, which is the quickest way to see whether chat features are on and what a verified sender looks like.