This might help
Product areas provide a similar function to the old forum areas and tags give a similar function to the sub forums.
edited to give a fuller explanation
In the old setup, we had fairly coarse-grained forums that would cover an area of the product, but there might be multiple different subjects people would talk about in that forum. For example, we had a single ‘2D’ forum that people could use to discuss sprites, tilemaps, 2D physics, etc; it was multiple different subjects being talked about, aggregated together into one forum. In some cases there was enough discussion about a specific subject that we set up sub-forums, to split the aggregation up.
In the new setup, we recognise each of those different subjects with tags, and the aggregation is done by what we call ‘product areas’ - predefined groups of tags that let you quickly see topics about related subjects in some part of the product. The old 2D forum contained discussions about sprites, tilemaps, 2D physics, etc - and the new 2D product area contains topics tagged with ‘sprite’, ‘tilemap’, ‘2D physics’, etc.
A topic can now appear in multiple product areas. In the old forum, if you wanted to ask about 2D physics, you might find yourself wondering whether to post in the ‘2D’ forum or in the ‘Physics’ forum. In the new setup, both the 2D and Physics product areas can include the ‘2D Physics’ tag and your topic will show up in both aggregations.
Does that help at all?
Some possibly useful info
On home page the tags under the main headers are selectable so you can jump directly to the filtered listing ( similar to how you could click a subgroup in the old Site)
You can also click the relevant tag under a post it will filter if you don’t want to use the drop down or add it to your personalised tag menu in the sidebar then you have a quick link direct to it