We now already understand the meaning of resistance, capacitance, voltage, and current. Every circuit needs some amount charge to flow in it to function. This need or requirement of current in the circuit is called current requirement. Whenever we apply a voltage to a circuit, the circuit uses/eats or draws current which is equal to voltage applied divided by the total resistance in the circuit. Or 1/R times the voltage applied where R is representative of resistance.
While building your circuit, sometimes you will realize that two different sensors in your circuit have two different types of current requirements; other times you have different voltage requirements. Think of this as the different tactics you use to avoid cleaning the room. In such conditions, we use resistors and capacitors in various combinations to get the desired results.