How to Send Instant Messages

Besides third-party apps, Messenger developed by Google gives you a real-time instant messaging service via Wi-Fi, 3G or 4G for Android users. To use this service and send an instant message from your Android device is pretty straightforward.
Tap the Messenger app icon.
Tap the plus sign and add a person or a group of people from your circles.
Add text or photos and tap the Send button.

Note: Messenger appears as a standalone app that comes with your Android system, or as a component of the Google+ app that can be downloaded from the Google Play store.