Discord

Discord is a community platform organized around servers, each divided into text and voice channels — a structure that came from gaming and now hosts communities of every kind.

What distinguishes it is persistent voice: channels stay open and people drop in and out, which supports the kind of ambient co-presence that scheduled calls do not. Combined with roles, permissions and bots, a server can run anything from a study group to a product support desk.

For products with technical or enthusiast users it has largely replaced the forum. The trade-off is that conversation is not indexed by search engines, so knowledge accumulated there is effectively invisible from outside.