This is part of a series of examples that describe the basic operation of the D3.js force layout.
…linkDistance tells the force layout the desired distance between connected nodes. It may seem strange that D3 doesn’t simply compel all links to be that distance. The force layout, however, takes other factors into account as well, which sometimes prevents it from achieving the exact link distance in all cases.
…charge, so named because it’s a property that acts like electrical charge on the nodes. With force-directed graphs in particular, charge causes nodes in the graph to repel each other. This behavior is generally desirable because it tends to prevent the nodes from overlapping each other in the visualization.