How do current and voltage vary in series and parallel circuits, respectively?

In a series circuit, the current is the same throughout; the voltage is split among the components (such as LEDs or resistors) in proportion to the resistance of the components (higher resistance means more voltage across that component). In a parallel circuit, the voltage is the same across each branch of the circuit. The current is split between each path and is inversely proportional to the resistance of the components on each path (higher resistance means a lower current in that path)