For any electronic circuit to function, you will need a power source.
In our case, a battery will play this role. It can come in a lot of different forms and characteristics. A battery delivers DC Current, meaning that the current only flows in one direction. It is commonly used to power laptops, mobile phones and other small electrical devices.
A battery is both a Voltage and Current source. To understand what it means, imagine electricity as water. Voltage would be the pressure provided by the battery to “push" the water throughout the circuit. So the higher the voltage is, the faster electricity flows through the circuit. Current would be the amount of water provided by the battery.
Current is measured in Amps (A) and Voltage is measured in Volts (V).