Groups help to organize and give structure to the board itself. If I'm doing a "Kitchen" (board) for the Jones (project), then I may create groups that look something like this....
Project Ideas
Faucet Options
Countertops
Sink Options
Hardware
etc., etc., etc. You can create as many groups as you'd like (scroll to the bottom of the board and click ADD NEW GROUP), rename them, and move items around easily in between them . If you're utilizing groups to the fullest, there's really no need for questions like "Where was this fabric being used?". If it's tucked nicely inside of the CUSTOM WINDOW TREATMENT FABRICS group, then everyone immediately is aware.
How to add a new group:
Click on the ADD GROUP icon at the top of any existing group. This will add a new group to the bottom of your board. You can then move groups as you wish.
You can also add a group from the bottom of your boards at any time.