Google's complete messaging app
Hangouts is Google's messaging app. With it you can chat to your Google contacts, and make voice and video calls to individuals or groups.
Why use Hangouts?
Do you need yet another messaging app? Hangouts has some advantages. Its best features are its Google account integration, and its excellent synced notifications. With Hangouts, notifications are synced immediately - it feels much more reliable than most apps in this sense. So if you're chatting in your browser, you won't see notifications on your phone every time you get a new message - but you can be sure you will get a notification if you have not read the message. Hangouts is way ahead of multiplatform apps like Skype in this sense. It's much more reliable.
Well designed and simple
The latest version has new sticker packs, and now allows you to see the last time your contacts were online. Like WhatsApp, you can turn this feature off, in your profile settings (annoyingly Hangouts will periodically ask you if you want to re-enable this). You can also easily share your location from Hangouts with a single tap, and set your status or mood for your contacts to see. One thing Hangouts lacks is access to your Google Drive files. But overall, it's a very usable messaging app.
A complete messaging app
If you use Google services like Gmail, Hangouts is really easy to get started with. It's a very complete messaging app, with text, SMS, video and audio calls, and more. Because you can also easily use it from your desktop browser and in Gmail, it's one of the most convenient messaging apps around.
As with most free messaging apps, there is a cost; here it's that your data is kept 'anonymously' by Google to help it provide you with tailored advertisements across its services.