Circuits are made using breadboards when temporary connections are
needed. These circuits are experimental. Making them is a way to learn
about electronics. You can reuse electronic components easily too. Much more about breadboards here.
To begin with we need a source of energy. A two-cell battery gives us
3 volts. But volts is not a measure of energy. The size of the battery
increases with energy but the volts may not. Voltage is a kind of force -
an electrical force that pushes electric current around.
Electric current flows from + (red) to - (black). Unfortunately this was decided before electrons were discovered and it is the negative electrons that actually move. Electrons move from - (black) to + (red)!
The simplest circuit is a conducting wire that connects + to - on a
battery. Don't do this! If you do this the mistake is called a "short
circuit" and the battery spends its energy on destroying itself! There
needs to be something in the circuit to limit the flow of electric
current to stop the battery destroying itself.
Here is a circuit with a number of objects which limit current and make the circuit interesting.
The 3V battery has a positive end (short bar) and a negative end (long bar). Moving anti-clockwise around the circuit, next is R1 a resistor. Resistors have a resistance measured in ohms and this one is 220 ohms. The Ω symbol (Omega) is shorthand for "Ohms". Resistors are used to limit current flow. Next is S1 - a toggle switch. This toggle switch can join 2 to 3 and stays "On" allowing current to flow. At the moment the switch is "Off". Finally we come to an LED (light emitting diode) which is red. This LED only needs 1.5V to make it light up so take care that the circuit uses the resistor to lower the voltage "seen" by the LED.
Here is what they might look like:
You will notice that the components have leads or bare wires coming from them. They have two - like the battery.
These leads can be pushed into holes in a breadboard so that the circuit shown can be assembled.
Can you make the red LED light up when you use the switch? You might like to try similar circuits here.