A design diagram refers to a particular type of circuit design which uses standard electrical/electronic symbols instead of pictures to show the way the circuit (or a part of it) works. Below is a typical 3-wire motor controller circuit using a typical momentary stop - start pushbutton channel employing a schematic diagram. (Momentary here means the button/switch you trigger will return to its default place once you physically let go of it, usually by a spring which forces the button/switch to do this.)
Think of it this way; a circuit structure is any sort of diagram that demonstrates how a circuit operates where the most important purpose is the appropriate wiring of components and their connection to each other rather than physical place relative to one another or planning prototypes. Nonetheless, in some applications classifying diagrams can be hard so do this as overall information. I've discovered this is particularly true when dealing with more complicated circuits and electronic equipment. I'm likely to use a simpler but typical industrial circuit because these circuit set ups are exactly the same, but yet where you're able to see how each sort of diagram indicates the role of the circuit in their own ways.
Pictorial schematic diagrams, or graphic circuit diagrams are basically the exact same thing with exactly the exact same function, but they use images of elements within the circuit rather than symbols. Again, here's the same specific circuit (virtually except a control transformer was inserted and they are utilizing conductors L1 and L3 instead of L1 and L2.
Less clutter? I have enough information in each one of these diagrams to know precisely what this circuit does and where to start looking for issues. Hope that this helps. ( Note: don't confuse circuit or schematic diagrams together with wiring diagrams; wiring diagrams will typically show images of components like the pictorial, and how the entire or part of a circuit will be wired. The difference is that wiring diagrams usually put an emphasis on real physical location of necessary components relative to each individual that basically tell a layman Just What to do about the wiring. )
Here's another schematic diagram demonstrating precisely the identical circuit, connections and components and it looks different but they both fall into exactly the same category.
Here is a technical variant of a schematic diagram. The major intent of this diagram will be to show the logic (speaking to electric control) of a circuit board. This diagram is the one that I mainly encounter in my line of work, and it is extremely successful for troubleshooting problems or learning how a circuit functions. Some circuits are so huge that most types of schematic diagrams need to be read in increments from book form (normally with coded numbers so that info can be easier located ). Again, here is the same precise circuit since the first two weeks, however looking at it in ladder type.