The Sankey chart type is a type of a flow diagram in which the width of the connecting lines is shown proportionally to the flow quantity between the nodes that those lines connect to.

Sankey diagrams are typically used to visualize the flow of energy, material, or cost transfers between entities. 

Sankey charts are specifically helpful in locating dominant contributions to an overall flow in the system.

Although it's not the primary use of Sankey, the following example illustrates use similar to the funnel chart. Here, we can see the flow of people who enter a building, go to the first floor, and enter offices 1a, 1f, and 1d. In the connecting links, we can spot the amounts of those movements: