A design diagram refers to a particular type of circuit structure which utilizes standard electrical/electronic symbols rather than images to show the way the circuit (or a part of it) works. Below is a standard 3-wire motor control circuit utilizing a normal momentary halt - start pushbutton channel employing a schematic diagram. (Momentary this means that the button/switch you trigger will return to its default position once you let go of this, typically by a spring that compels the button/switch to do this.)
Think of it in this way; a circuit structure is any kind of diagram which demonstrates the way the circuit operates where the principal purpose is that the appropriate wiring of elements and their relationship to each other rather than physical location relative to each other or intending prototypes. However, in some uses classifying diagrams can be challenging so choose this as overall advice. I have found this is particularly true when working with much more complex circuits and electronic equipment. I'm going to use a more straightforward but average industrial circuit because these circuit set ups are the exact same, but where you can see how each type of diagram shows the operation of the circuit in their own manners.
Here is a specialized version of a schematic diagram. The most important point of this diagram will be to demonstrate the logic (speaking to electrical management ) of a circuit board. This diagram is the one I mainly encounter in my own line of work, and it is extremely effective for troubleshooting issues or learning the way the circuit works. Some frequencies are so huge that many types of schematic diagrams need to be read in increments in novel form (normally with coded numbers so that info can be easier located ). Again, here's the same exact circuit as the first two, but considering it in ladder shape.
Less clutter? I've got enough information in each one of these diagrams to know precisely what this circuit does and also where to look for issues. Hope that this helps. ( Note: do not confuse lecture or circuit diagrams together with wiring diagrams; wiring diagrams will typically demonstrate images of components such as the pictorial, and also the way the entire or portion of a circuit will be wired. The difference is that wiring diagrams generally place an emphasis on real physical location of necessary components relative to each individual that essentially tell a layman Just What to do about the wiring)
Here's another schematic diagram demonstrating exactly the same circuit, connections and components and it looks different but they fall into exactly the same category.
Pictorial design diagrams, or pictorial circuit diagrams are essentially the same thing with exactly the exact same function, however they use pictures of components inside the circuit instead of symbols. Again, here's the exact specific circuit (virtually except a controller was inserted and they're utilizing conductors L1 and L3 instead of L1 and L2.