It doesn't mean anything immediate for the average player, but for modders with knowledge with things like C++, they can expand the engine considerably since it provides a strong base for creating "trainers" (such a pathetic term, lets go with "game modules").

The ability to create new tag groups is there so the programmers of modding teams can support their designer's ideas without having to hard code data into their Yelo game module.

We're not releasing the exact details on whats included in the Yelo source, as open sourced features may come and go before the release date, which again, is not today.