From Hammer & Chisel Inc.:
All-in-one voice and text chat for gamers that's free, secure, and works on both your desktop and phone. Discord is always completely free to use with no gotchas. This means you can make as many servers as you want with no slot limitations.
Encrypted server to client communication keeps your IP address safe. Stop getting ganked because you're logged into Skype.
Our resilient Erlang backend running on the cloud has built in DDoS protection with automatic server failover.
Easily share images, videos, and links from your desktop or phone. Discord embeds most types of media directly in the chat.
GIFs only play when you mouse over them, so your CPU is spared.
Designed for use while gaming, Discord has minimal impact on your CPU. Your game's performance won't be affected in the slightest.
It takes just 10 seconds and doesn't require any drivers or weird setting configuration. Discord can even run in the browser which is great for PUGs you invite to your voice channel or those stubborn friends of yours.
Discord is built with the latest tech using a modern jitter buffer, automatic gain control, noise suppression, echo cancellation, system attenuation on Windows and more.