Hey readers I’m Mechaila and I will be explaining what is a circuit diagram.
A circuit diagram is a electrical circuit drawing to explain it is also a path to let electric flow 
For example this Is a simple diagram
How to make a circuit diagram?? so first you sketch it first then grab a battery that can work the bigger the battery is the better it will work then next find a switch and wires that you can connect it and a bulb. and search for a tutorial on how to make one.