General seems to be for discussions about the world of OpenSim, excluding help requests and OpenSim itself, i.e. development or grid operation.
Help seems to be for help topics regarding the world of OpenSim, excluding OpenSim itself, i.e. development or grid operation.
OpenSimulator seems to be for the software itself and therefore only interesting if you're either a grid admin or an OpenSim developer, or if you want to use OpenSimWorld to try and get into contact with developers.
Satyr Farm is for the Satyr Farm, discussions as well as help.
Support seems to be on-site support for OpenSimWorld itself a.k.a. Ask Satyr.
Apart from the forums, there are also the groups; see the link right below or here:
https://opensimworld.com/groups The groups are not only user groups, but also specialised discussion forums founded and operated by OpenSimWorld users. This means that anyone can start a group on a topic if it's worth starting one.