You can organize messages, interests, subscriptions and filters into groups.
Groups are more than just a way to organize similar items. You can report on messages that are in the same group while interest and subscription groups are used to show items on forms (for example in dropdown selectors).
Groups appear in the sidebar.
You can create a new group by clicking the "New group" option.
To move items into groups select items you wish to move, then click the "Move" button.
You can have nested groups.