Components

Components are used in circuits for electricity to flow, and we write these components via symbols.

Firstly, we write multiple vertical lines to depict a Cell or Battery, which powers the circuit.

Wires are written as lines and normally straight, and they carry the current throughout the circuit.

A Fuse is a rectangle with a wire running through it. Its purpose is to prevent the device from being overloaded. When too much power flows through the circuit, the fuse breaks, cutting power.

For switches, it will look like two circles connected via a short line between them, when the line is connected it means the current can flow, but when the switch's line isn't it means the current can't flow.

Then a Diode is a component that only allows current to flow a certain way, a form of diode is a Light Admitting Diode or LED, which lights up when electricity flows through it.

Now, for measuring current, we have Ammeters, which are put in series or connected through the circuit, and Volumeters, which are used for measuring potential difference and are  added in parallel, usually outside the circuit.

Lastly, we have resistors, which 'resist' the current to a specified amount, certain components can only function at certain amounts of electricity, if we put too much power into a component it might fry the circuits and the components might smoke or catch on fire, for example, when you charge your phone, it has resistors in the plug to not take too much power so that the internals don't fry.
Along with normal basic resistors, there are also variable resistors that can be modified so that they resist more or less current based on the situation.

Light-dependent resistors use light as a way of varying the amount of resistance, if you put them in a bright environment will resist a lot less than in a dark one as the darker it gets the more they will resist an application many people use these LDR's is in automatic nightlights which turn on when the lights in the room are off.

Thermistors use heat to vary the resistance so the more heat the less resistant the resistor becomes, and the colder it gets the more resistant it becomes.