When someone sends you an SMS or IM, you see their name if they are in your contacts list, and the name of the app that was used to send it, for example WhatsApp.
Voice control announces the message and asks if you want it to be read aloud.
Select Read Aloud to have it read to you by your device.
If you selected the message itself, you see the following options:
Call - select this button to make a hands-free call to the sender of the message. (Android phones only.)
Reply - select this button to reply using a predefined message such as Sorry, can't talk now. (Android phones only.)
Read Aloud - select this button to have the message read aloud.