The announce category holds announcements and discussion of new releases and features.
Discussion about features or potential features of syncthing: how they work, why they work, etc.
Tips and tricks for getting things running smoothly.
Use the support category to ask for help or if you have general setup questions.
This category is for topics related to hacking on syncthing: submitting pull requests, configuring development environments, coding conventions, and so forth.
This category is for describing how you use syncthing. This gives the developers a feeling for what's going on, and may give other users ideas and hints.
General is the "none of the above" category... If it's not something you need help with, it's not a discussion about a new feature, it's not a how-to guide, then maybe it fits here.
Discussion about this forum, its organization, how it works, and how we can improve it.