Can you specify the version of Campaign you are using?
In a general manner, you can consider a campaign to be only a hierarchy item so you can better organize your marketing activities:
Hope this helps,
Let me know what your version of Campaign is (Standard or Classic) and I'll be able to give you more details and link some relevant resources if you need.
In short, a delivery template is a template for 1 delivery, while a campaign template is a template for several objects like deliveries or workflows, all together.
Hope this makes sense.