The current flowing in a series circuit is the same everywhere.
Parallel circuits have more than one loop.
An electron will not pass through every component on its way round the circuit. The diagram shows a circuit with two bulbs in parallel.
If one of the bulbs is broken, the current can still flow round the circuit through the other loop, so the other bulb stays on.
The lights in a house are wired this way. If one light breaks, the others continue to work. If the lights were wired in series instead, all the lights would go out if one breaks. In a parallel circuit, measurements of the current at different points in the circuit should add up to the ammeter reading close to the cell.
In the circuit above:
Since energy has to be conserved, the energy transferred around the circuit by the electrons is the same whichever path the electrons follow. This means that the potential difference across the components in a parallel circuit is always the same value.