The analogy I’ll be using for this discussion is the toll booth  analogy. It can actually be applied to both series and parallel  circuits, but I’ll only address the former now. In this analogy, traffic  represents current and a toll booth represents resistors (or  resistance). Imagine traffic flowing on a busy highway and the highway  authority adds a toll booth. The flow rate would slow down as drivers  have to stop or slow down to pay the toll. The same can be said for  current as it passes through a resistor. In a series circuit, with each  subsequent resistor, resistance increases and the flow rate slows. If  more toll booths are continuously added in a series, the “resistance”  would increase as the traffic continues to back up with each subsequent  toll booth added. Traffic therefore slows down overall. This is  representative of current, which slows down over time in a series  circuit.

References:

Physics Classroom. (n.d.). Physics Tutorial: Two Types of Connections. https://www.physicsclassroom.com/class/circuits/Lesson-4/Two-Types-of-Connections