Think of it this way; a circuit diagram is any kind of diagram that demonstrates the way the circuit functions where the primary purpose is the appropriate wiring of elements and their relationship to each other rather than physical location relative to one another or intending prototypes. However, in some applications classifying diagrams can be hard so accept this as general information. I have discovered this is particularly true when working with more complicated circuits and electronics. I'm likely to work with a more straightforward but average industrial circuit because these circuit setups are exactly the same, but nevertheless where it is possible to see how each sort of diagram shows the purpose of the circuit in their own ways.
Here's another schematic diagram demonstrating precisely the same circuit, components and connections and it seems different but they both fall into exactly the identical category.
A schematic diagram refers to a specific sort of circuit structure which uses standard electrical/electronic symbols rather than pictures to demonstrate the way the circuit (or portion of it) functions. Below is a typical 3-wire motor control circuit utilizing a standard short stop halt - start pushbutton channel working with a schematic diagram. (Momentary here means the button/switch you trigger will go back to its default place once you physically let go of it, usually by a spring that compels the button/switch to do this.)
Here is a variant of a schematic diagram. The primary aim of this diagram is to show the logic (referring to electrical control) of a circuit board. This diagram is the one I mostly encounter in my line of work, and it's very successful for troubleshooting problems or learning the way the circuit functions. Some frequencies are so enormous that many kinds of schematic diagrams have to be read in increments in book form (generally with coded numbers so that information can be simpler located ). Again, here's the exact exact circuit because the first two, but looking at it in ladder type.
Pictorial design diagrams, or pictorial circuit diagrams are essentially the same thing with exactly the same function, however they use images of components within the circuit rather than symbols. Again, here's the identical exact circuit (almost except a control transformer was included and they're utilizing conductors L1 and L3 instead of L1 and L2.
Less clutter? I have enough info in every one of these diagrams to know just what this circuit will do and where to search for problems. Hope that this helps. ( Note: do not confuse circuit or schematic diagrams with wiring diagrams; wiring diagrams will typically demonstrate pictures of components like the pictorial, and how the whole or portion of a circuit is wired. The difference is that wiring diagrams typically put an emphasis on real physical location of necessary elements relative to each individual that basically tell a layman Just What to do concerning the wiring)