Consider it in this way; a circuit structure is any sort of diagram that illustrates how a circuit functions where the most important objective is that the appropriate wiring of elements and their connection to each other instead of physical place relative to each other or planning prototypes. Nevertheless, in some applications classifying diagrams can be hard so consider this as overall information. I've found this is particularly true when dealing with more complicated circuits and electronic equipment. I'm likely to use a more straightforward but average industrial circuit because these circuit setups are exactly the same, but yet where you can observe how each kind of diagram indicates the function of the circuit in their own ways.
A design diagram refers to a specific type of circuit diagram that utilizes standard electrical/electronic symbols rather than pictures to demonstrate how a circuit (or a portion of it) functions. Below is a standard 3-wire motor control circuit using a typical short stop stop - start pushbutton channel working with a schematic diagram. (Momentary here means that the button/switch you trigger will go back to its default position once you physically let go of this, usually by a spring which forces the button/switch to get this done.)
Pictorial design diagrams, or pictorial circuit diagrams are basically the identical thing with the same purpose, however they use pictures of elements within the circuit instead of symbols. Again, here is the same specific circuit (virtually except a control transformer was inserted and they are using conductors L1 and L3 rather than L1 and L2.
Here's a variant of a diagram called a ladder diagram. The main intent of this diagram will be to demonstrate the logic (speaking to electrical control) of a circuit board. This really is the one I mostly come across in my own line of work, and it's extremely successful for troubleshooting issues or learning the way the circuit works. Some frequencies are so huge that many kinds of schematic diagrams have to be recorded in increments from novel form (normally with coded numbers so that information can be simpler found). Again, here is the exact same exact circuit since the first two weeks, but looking at it in ladder form.
Right, much less mess? I have enough information in each these diagrams to know exactly what this circuit will do and also where to start looking for issues. Hope this helps. ( Note: don't confuse circuit or schematic diagrams together with wiring diagrams; wiring diagrams will typically demonstrate images of elements like the pictorial, and also the way the whole or portion of a circuit is wired. The difference is that wiring diagrams usually put an emphasis on actual physical location of necessary components relative to each other that basically tell a layman exactly what to do concerning the wiring)
Here is another schematic diagram showing the same circuit, components and connections and it seems different but they both fall into exactly the identical category.