Groups are used to tie all of your hubs on a particular topic together. With a quick glance at your profile, I thought of at least three groups - writing, literature, and relationships.
Under the "hub" tab in your account, click on "groups". Once there, click on "add new group". Create a name for your group. Repeat that step to create as many groups as you need for your various topics. Once you've created the groups, scroll down the screen until you find the titles of your hubs. Now simply click and drag the title to place it under the appropriate group.
The next time you view one of your published hubs, you'll see a "previous" and "next" button under the hub. If the person has just read one of your hubs about relationships, they can click either of those buttons to navigate through all of your hubs about relationships without having to go back to your profile and search the main hub list.
I'm not sure if there's a limit on how many groups you can have, but I have eight or ten.