Discord is a social network launched on May 13th, 2015. With over 250 million users, it's among the fastest growing social networks in the world, tripling its user count in one year in 2018.
Discord allows users to create customized "servers" to use for instant messaging and VoIP communication, in a similar way to Skype, Slack, and TeamSpeak. These servers can be fully customized and sorted into categories, allowing them to be used for a wide variety of topics. Users can also be given different permissions, allowing for staff hierarchy. With Nitro Boosting, more features for favored servers among users can allow for even more features, such as GIF Server Icons.
Relevance to Super Smash Bros.
The nature of Discord allowed it to quickly grow a staple Smasher userbase, with players creating servers dedicated to numerous parts of the game. Many of these are dedicated to singular characters, regions and tournament circuits. This allows for more focused discussion than on places such as SmashBoards.
One platform that gave a significant rise to this is SmashCords, a website compiling relevant Smash-themed Discord servers. It also has a dedicated bot to further aid Smash-related communication known as "Floof Bot", which has since become a standard addition in many Smash-centric Discord servers. Most "SmashCords" have very large amounts of members, with the Joker Discord server having over 14,000 members as of June 2020.
Many top players such as MkLeo have their own Discord servers with relatively high popularity. This allows them to connect with their fanbase, such as through promoting streams on Twitch and giving more direct subscriber perks. This trend has spread to many other areas of the Smash Community, such as GimR running his own tech-centric Smash Discord.