Location commands are those that deal with defining a location on a
page. The basic command
\node{nodename}{object}
Each node has its name, height, width, and the location of the lower
left hand corner point passed down to postscript where it will remain
until needed. Note that the object will be printed by TEX but the
lines drawn by Postscript. A variant
of this command is
\nodepoint{nodename}[horizontal displace][vertical displace]
The node's height and width are 0pts, but the location can be
displaced.