A flow network is a directed graph where each edge has a capacity. The capacity is the maximum amount that can flow from node to node . There are two special nodes: the source (where flow originates) and the sink (where flow ends). All flow starts at the source and ends at the sink. No flow leaks out anywhere else. Think of it like a water system: the source is a reservoir, the sink is a drain, and each pipe has a maximum throughput.
Your goal is to push as much water as possible from source to sink.