[insoluble]

Since designers are presumably aware of things like Photoshop and related technologies, it could be useful to explain by analogy. For example, a framework could be said to have "macros" that apply various types of "effects" and interaction to elements on the page. Frameworks also provide "layers or pieces of templates" (think responsive columns) that make aligning elements more uniform and consistent throughout the site. Another thing to note to the designers is that the original languages for making pages were very cryptic and tedious while modern frameworks take away a good part of the tedium by simplifying the layout and element-interaction processes.

Edit: By "designer", I was thinking you meant graphics designer; I apologise if you meant something else.