In the simplest words conceivable, a series circuit provides the current of electricity with a single optimal path through the maze of resistance. Parallel circuits, on the other hand, are constructed in such a way that the current can travel down two or more routes through the circuit. Parallel circuits are distinguished from series circuits by the fact that the branching path of the current travels alongside itself as it passes through both loops at the same time.
In parallel circuits, the behavior of the current as it flows through the circuit is largely dictated by the fact that an electric current will seek out the lowest-voltage portions in a system and occupy these areas in whatever manner it is able to do.
It's not quite that straightforward, but you'll be relieved to know that there are only a handful of extra rules to consider in this situation. What exactly determines the path of least resistance for a current is a mystery.
I hope this helps you
:)