3. Types of circuits.

3.1. Series circuit.
Two or more elemts form a series circuit when the output of one element provides the input for the next element.
In the following diagram, the same current flows through all the elements, and the total voltage is the sum of the tensions at the end of each element.

3.2. Parallel circuit.
In a parallel circuit, the various components share the same input and output. In other words, the wires from both sides are joined together. In this case, the potential difference is the same for each element, but the current that flows through each brach is different.

3.3. Combination circuit.
A combination circuit has some elements connected in series and other elements connected in parallel.
In this tuype of circuit, the current remains constant between elements that are connected in series.