@mrtoad Cuttle is a fully featured vector editor (like Illustrator or Inkscape). You can store up to 5 of your own projects on a free account. Projects can be either be started from blank or by making a copy (“remix”) of a project shared by the community (like on our Explore or Templates pages).
A download is any time you download an SVG file (or PDF, PNG, or File > Print). Free accounts get 10 downloads per month.
Note you can use a template, customize it, and download without needing to create a new project. You only need to create a project if you want to further edit the design in the Cuttle editor, for example: adding some text to a box, cutting some holes on a side, etc.
If you’re just making a few boxes using the free box templates, the free account should suffice! Pro is for people making lots of designs or if you want access to the premium templates (e.g. Hinged Lid Box).