Chat was the first thing to follow after the creation of the email protocols and clients. 
Originally there was IRC and then that expanded. 


- There is now [IRC OFTC](https://www.oftc.net/WebChat/) (The Open and Free Technology Community) as well, aka WebChat
- [Linen.dev](https://www.linen.dev) is an interesting alternative to chat which incorporates both Discord and Slack messages and also has [forum](https://www.linen.dev/s/linen/c/blog) features. 
- [Slack](https://slack.com) 
- [Discord](https://discord.com) 
- [Google Chat ](https://mail.google.com/chat/u/0/)
- [Whatsapp](https://whatsapp.com)/Facebook messenger
- [Apple iMessage ](https://mymessage.apple.com/mmuser/)
- SMS for texting 
- [Signal](https://signal.org/download/) 
- [Telegram](https://telegram.org) 
- [Line](https://line.me/en/) 


Forums: 
- [Zulip](http://zulip.com) 
- [Discourse](https://discourse.org) 
- [Quora](https://nl.quora.com) 
- [Lemmy](https://join-lemmy.org)