Some things in Firefly III can be divided into groups. At the moment this applies only to piggy banks, but the list is slowly growing.
Groups are a very basic visual divider of objects. For piggy banks, you could divide them up into two groups: "large savings" and "small things".
There are dedicated pages (listed under
/groups/index) to edit and delete groups. You cannot create groups on this page; groups are created whenever you edit an object and set a group.
Groups are automatically deleted when no objects exist in the group. If you remove the final object from a group (for example, a single piggy bank) the group is gone.
This feature is pretty new and for the time being, you can't do much with them. If you have good ideas just let me know on GitHub!