Content editors can create, edit, and schedule content. Within the content, they can

- change the videos in an element

- change the images in an element

- edit text, its size and alignment within a text element

- upload files on the server and use them in content

Template creators can do all the same this, but additionally, they can

- add and remove elements (such as images, text or html)

- change the url in an html-element

- re-size and move elements

- change the font and color of texts

- change the color, opacity and shape of the rectangle

Moreover, they can design and save templates: what elements they contain, as well as their location within the template, their size and their color. Those templates are then used by content editors when they want to make content for the screens.

See also I can't edit content/a template.