This is the default example of the loom plugin which creates a chart with a group of entities in the center and different group of entities on the outside. They are connected by strings where the thickness of the string on the outside represents the connection (i.e. value) of the inner and outer entity.
For example, in this case, the inner entities are the characters of the Fellowship in the Lord of the Rings movies. The outer entities are the locations in Middle Earth where the movie takes place. The connection/value is the number of words spoken by each character at each location.
Read more about the loom chart layout / plugin for d3 here
A more advanced version that also uses interactions can be found here
Built with blockbuilder.org