You are confused? Welcome to Tumbleweed!
Tumbleweed is a rolling distro and it is rolling fast, so documents usually lag, but there is still hope…
For instance there is excellent documentation about SUSE products, see for instance SLES-systemd-basics: some details might not strictly apply to Tumbleweed but if you want to learn something about systemd in (open)SUSE that is a great starting point.
Then there is https://en.opensuse.org/Portal:Wiki where you can search almost anything technical about the several openSUSE products and releases; often that is the first line of documentation when something important changes in Tumbleweed.
Then if you know which command you need, the details are usually in man <command> or <command> --help but likely you already know that.
And last but not least, ask here on the Forums, we are here to help (everybody here was new to Tumbleweed once upon a time…)
And, and, if you are brave enough, the technical news usually land on the factory@lists.opensuse.org mailing list, where developers discuss their stuff.