Discord is an application much like Teams or Zoom; a way for people to come together in groups. It has a chat function, as well as voice and video call capabilities. While originally it was a good gathering place for those who were playing online multiplayer video games, it has exploded to draw all sorts of people and interests on the platform. You can use the application through an internet browser or have the application downloaded to your PC &/or mobile phone.
It is available on Apple, Microsoft, and Linux devices, both desktop and mobile.