Recs.
Updated
Discord is a free-to-use VoIP and instant messaging app targeted primarily at gaming communities.
SpecsUpdate
Pros
Pro Simple & Appealing UI
The interface is very easy to follow - you have three sections. On the left are the channels for your server, which you can quickly and easily switch between. The large section in the middle is the main chat area, where each message has the person's username, avatar (or image), and timestamp. On the right is a list of all the people in the chat, where it also ways what games each person is playing (if applicable and set up by the user).
Pro Bots integration
You can use bots to control your server like welcome message, banned words, when your Twitch account goes online and many others.
Cons
Con No dedicated servers
You are sharing server bandwidth with every other discord user. Meaning if you are using discord and need voice coms for say example your guild is raiding something, and every other discord user on the planet decides to log on YOUR guilds raid is going to suffer because you don't have dedicated bandwith discords overall performance will suffer immensely.
Con Financial scam
The owner and CEO of Discord Jason Citron has secured nearly 20 million in investment funds for Discord. Discord is something that is free it is not a money making machine. Currently the only way Discord is staying afloat is by continually securing new investor funds. Jason Citrons track record shows a pattern of starting a business attracting large investors then walking away with the company bankrupt or sold and his pockets filled. 20 million dollars would have produced a product light-years better than discord, something fishy is going on.