Dot is a text format used to describe directed graphs. It is used by Graphviz and other tools that deal with graphs. There are many tools that can be used to view a dot file visually as a directed graph. The simplest of these tools is XDot.
$ sudo apt install xdot
$ xdot foo.dot
You can zoom in and out on the graph to understand its architecture.
Tried with: xdot 0.4-2 and Ubuntu 12.04 LTS