InfoQ has a nice rundown of all that GitHub announced at Satellite this week. On Codespaces:
Codespaces gives you a fully-featured, cloud-hosted dev environment that spins up in seconds, directly within GitHub, so you can start contributing to a project right away.
At the heart of Codespaces lies Visual Studio Code running in your browser, so you get code completion, extensions, code navigation, and the rest of Visual Studio Code features you are used to.
GitHub Discussions appear very similar to Issues and Pull Requests on the outside, but they aim to go beyond the linear structure of the latter by supporting a threaded questions and answers format. According to GitHub, this should make it easier to organize an otherwise unstructured conversation and build a persistent knowledge base.
I’m personally not too excited about either of these features. I think Codespaces could be a big deal for casual contributions, but those are the lowest form of contribution. Discussions seems like a direct shot at StackOverflow, which makes good business sense, but I wonder if it will get mired in the Issues/Pull Requests/Wikis mucky muck.