If you create a lot of emails, you can group them into categories so they are nicely organized. You can add categories to keep your templates, messages, or campaigns in order.
If you go to "Campaigns" -> "Email", you will see the default category "Single recipient". Campaigns with only one recipient are automatically assigned to this category.
How to create a category
Go to "Campaigns" -> "Email". On the bottom left of the window, under Campaign list, you will see a menu Categories.
Simply, click on + Add new.
Group them any way you'd like: newsletters, pricing, promotions, marketing, follow-ups, etc.
You can also find "Categories" in the section "Docs" -> "Categories".